Light emission drive circuit and its drive control method and display unit and its display drive method

ABSTRACT

A light emission drive circuit includes an electric charge accumulating section for accumulating electric charges on the basis of a gradation sequence signal designating a luminance gradation sequence. A light emission control section flows a light emission drive current having a current value in accordance with an amount of the electric charges accumulated in the electric charge accumulating section. A writing control section controls a supplying state of the electric charges based on the gradation sequence signal to the electric charge accumulating section on the basis of a first control signal. A voltage control section controls a drive voltage for operating the light emission controlling section on the basis of a second control signal.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based upon and claims the benefit of priority fromprior Japanese Patent Applications No. 2004-360105, filed Dec. 13, 2004;No. 2004-368031, filed Dec. 20, 2004; and No. 2004-368850, filed Dec.21, 2004, the entire contents of all of which are incorporated herein byreference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an emission drive circuit and its drivecontrol method and a display unit and its display drive method.Particularly, the present invention relates to a light emission drivecircuit that can apply a current control type (or a current drive type)of light emission element emitting light at a predetermined luminancegradation sequence by supplying a current in accordance with the displaydata to plural display panels (pixel arrays) and its drive controlmethod, and a display unit provided to each display pixel and itsdisplay drive method.

2. Description of the Related Art

In recent years, as a monitor and a display of a personal computer and avideo system, a display device in place of a conventional display unitapplying a conventional cathode-ray tube (CRT) has been widely used.Particularly, a liquid crystal display (LCD) has been rapidly widespreadbecause it can be made thinner, lighter, spacious, and lower-powerconsumption or the like, in comparison with the conventional display. Inaddition, a relatively small liquid crystal display has been also widelyapplied as a display device that has been remarkably widespread inrecent years such as a cellular phone, a digital camera, and a personaldigital assistance (PDA).

As a next-generation display device (display) following such a liquidcrystal display, a full-scale commercial viability and diffusion of alight emission element type of display device, in which an organicelectro luminescence (hereinafter, abbreviated as “an organic ELelement”) and an inorganic electro luminescence (hereinafter,abbreviated as “an inorganic EL element”) or a light emission element (aself-luminous type of a display pixel) such as a light emission diode(LED) are arranged in a matrix, has been expected.

Particularly, in comparison with the above-described liquid crystaldisplay, the light emission element type of display applying an activematrix drive system has a higher display response speed, no viewingangle dependency, a high luminance, a high contrast, and a highresolution of a display image quality or the like. Further, the lightemission element type of display does not need a back light as theliquid crystal display. Therefore, the light emission element type ofdisplay has a very superior characteristic such that it can be madefurther thinner and lighter and a low-power consumption is possible.

In such a light emission element type of display, various drive controlmechanisms and control methods for controlling the operation of thelight emission element (the light emission state) are suggested. Forexample, as described in Jpn. Pat. Appln. KOKAI Publication No.8-330600, there has been known a configuration including a drive circuitprovided with a plurality of switching elements for light-emission-drivecontrolling the light emission element (hereinafter, abbreviated as “alight emission drive circuit”) for each display pixel to compose adisplay panel in addition to the above-described light emission element.

FIG. 22 is a schematic block diagram showing a substantial part of avoltage control active matrix light emission element type of displayaccording to the prior art. FIG. 23 is an equivalent circuit diagramshowing a constitutional example of a display pixel (a light emissiondrive circuit and a light emission element) that can be applied to alight emission element type of display according to the prior art. Here,in FIG. 23, the circuit configuration provided with an organic ELelement as the light emission element is shown.

An active matrix type of organic EL display unit described in Jpn. Pat.Appln. KOKAI Publication No. 8-330600, as roughly illustrated in FIG.22, is configured so as to comprise: a display panel 110P in which aplurality of display pixels EMp are arranged in a matrix in the vicinityof each intersecting point of a plurality of scan lines (a selectionline; a signal line in a Y direction) SLp arranged in row and columndirections respectively and a data line (a signal line; a signal line ina X direction) DLp; a scan driver (a Y directional peripheral drivecircuit) 120P connected to each scan line SLp; and a data driver (a Xdirectional peripheral drive circuit) 130P connected to each data lineDL.

Each of display pixels EMp, as shown in FIG. 23, is configured so as tohave: a light emission drive circuit DCp including a thin filmtransistor (TFT) Tr 111 in which a gate terminal is connected to thescan line SLp and a source terminal and a drain terminal are connectedto the data line DL and a contact point N111 , respectively, and a thinfilm transistor Tr 112 in which the gate terminal is connected to thecontact point N111 and a predetermined power source voltage Vdd isapplied to the source terminal; and an organic EL element (a currentcontrol type of a light emission element) OEL in which an anode terminalis connected to the drain terminal of a thin film transistor Tr 112 ofthe light emission drive circuit DCp and a ground potential Vgnd that isa lower potential than the power source voltage Vdd is applied to acathode terminal. Here, in FIG. 23, reference symbol Cp denotes acondenser to be formed between the gate sources of the thin filmtransistor Tr 112.

In the display unit including the display panel 110P configured by thedisplay pixel EMp having such a structure, first, an on-level scansignal voltage Ssel is sequentially applied from the scan driver 120P toeach scan line SLp, whereby the thin film transistor Tr 111 of thedisplay pixel EMp (the light emission drive circuit DCp) for each row isturned on and the display pixel EMp is set at a selection state.

By applying a gradation sequence signal voltage Vpix in accordance withthe display data to the data line DLp of each row by a data driver 130Pin synchronization with this selection timing, a potential correspondingto the gradation sequence signal voltage Vpix is applied to the contactpoint N111 (namely, the gate terminal of the thin film transistor Tr112) via the thin film transistor Tr 111 of each display pixel EMp (thelight emission drive circuit DCp).

Thereby, the film transistor Tr 112 is turned on in a conducting statein accordance with the potential of the connect point N111 (namely, aconducting state in accordance with the gradation sequence signalvoltage Vpix). Then, a predetermined light emission drive current issupplied from the power source voltage Vdd to the ground potential Vgndvia the thin film transistor Tr 112 and the organic EL element OEL, andthe organic EL element OEL performs the light emission operation at aluminance gradation sequence in accordance with the display data (thegradation sequence signal voltage Vpix).

Next, by applying an off-level scan signal voltage Ssel to the scan lineSLp from the scan driver 120P, the thin film transistor Tr 111 of thedisplay pixel EMp for each row is turned off, the display pixel EMp isset at a no-selection state, and the data line DLp and the lightemission drive circuit DCp are electrically shielded. In this case, whenthe potential applied to the gate terminal (the contact point N111) ofthe thin film transistor Tr 112 is kept in the condenser Cp, apredetermined potential is applied between the gate sources of this thinfilm transistor Tr 112, and this results in that the thin filmtransistor Tr 112 is kept in the on state.

Accordingly, as same as the light emission operation in theabove-described selection state, a predetermined light emission drivecurrent is supplied from the power source voltage Vdd to the organic ELelement OEL via the thin film transistor Tr 112 and the light emissionoperation continues. The light emission operation is controlled so as tobe continued, for example, on one frame till the gradation sequencesignal voltage Vpix corresponding to the next display data is applied(written) in the display pixel EMp of each row.

Such a voltage drive control method is called as a voltage gradationsequence designation system (or a voltage gradation sequence designationdriving) because the current value of the light emission drive currentto be supplied to the organic EL element OEL is controlled bycontrolling the voltage value of the voltage (the gradation sequencesignal voltage Vpix) to be applied to each display pixel EMp(specifically, the gate terminal of the thin film transistor Tr 112 ofthe light emission drive circuit DCp) so as to perform the lightemission operation at a predetermined luminance gradation sequence.

The display unit in which the light emission drive circuit correspondingto the voltage gradation sequence designation system is provided to eachdisplay pixel involves the following problem.

In the light emission drive circuit DCp as shown in FIG. 23, a currentpath is connected to the organic EL element OEL in series and theoperation property (particularly, the threshold voltage value property)of the thin film transistor Tr 112 for the light driving to supply thelight drive current corresponding to the display data (the gradationsequence signal voltage) is changed (temporarily changed) depending onthe usage time or the like. In such a case, the current value of thelight emission drive current (the current between the source and thedrain) flowing between the source and the drain at the predeterminedgate voltage (the potential of the contact point 111) is varied (forexample, decreased). For this reason, it becomes difficult to stablyrealize the light emission operation at the appropriate luminancegradation sequence in accordance with the display data for a long time.

In addition, in the case where the element properties (the thresholdvoltage property) of the thin film transistors Tr 111 and 112 within thedisplay panel 110P are variable for each light emission drive circuitDCp or in the case where the element properties of the thin filmtransistors Tr 111 and 112 are variable for each display panel 110Pdepending on a production lot, the above-described variation of thecurrent value of the light emission drive current becomes large in thelight emission drive circuit of the voltage gradation sequencedesignation system. For this reason, the appropriate gradation sequencecontrol cannot be carried out and the display image quality is lowered.

BRIEF SUMMARY OF THE INVENTION

An object of the present invention is to provide an emission drivecircuit capable of realizing the operation for light-emission driving alight emission element at an appropriate luminance gradation sequence inaccordance with the display data by supplying a light emission drivecurrent having a current value in accordance with the display data andits drive control method and a display unit having a good display imagequality and its display drive method.

According to a first aspect of the present invention, there is provideda light emission drive circuit for supplying a light emission drivecurrent to make a light emission element perform light emission,comprising:

an electric charge accumulating section for accumulating electriccharges on the basis of a gradation sequence signal designating aluminance gradation sequence;

a light emission control section for flowing a light emission drivecurrent having a current value in accordance with an amount of theelectric charges accumulated in the electric charge accumulatingsection;

a writing control section for controlling a supplying state of theelectric charges based on the gradation sequence signal to the electriccharge accumulating section on the basis of a first control signal; and

a voltage control section for controlling a drive voltage for operatingthe light emission controlling section on the basis of a second controlsignal.

According to a second aspect of the present invention, there is provideda light emission circuit comprising:

a selection line;

a hold line;

a data line;

a supplying voltage line;

a hold transistor having a gate electrically connected to the hold line,and a current path;

a drive transistor having a gate and a current path, the gate of thedrive transistor being electrically connected to one end of the currentpath of the hold transistor and one end of the current path of the drivetransistor being connected to the supplying voltage line; and

a selection transistor having a gate and a current path, the gate of theselection transistor being electrically connected to the selection line,one end of the current path of the selection transistor being connectedto the other end of the current path of the drive transistor, and theother end of the current path of the selection transistor beingconnected to the data line.

According to a third aspect of the present invention, there is provideda drive control method of a light emission drive circuit, which suppliesa light emission drive current to a light emission element to make thelight emission element perform the light emission, comprising:

setting a first potential difference equivalent to a threshold value ofa transistor element, or a first potential difference equivalent to theminimum luminance voltage necessary for generating the light emissiondrive current required for making the light emission element perform thelight emission operation at the minimum luminance gradation sequencebetween a gate and a source of a transistor element to supply the lightemission drive current to the light emission element;

applying a gradation sequence signal to make the light emission elementperform the light emission operation at a luminance gradation sequenceto the transistor element and setting a second potential difference inaccordance with the luminance gradation sequence between the gate andthe source of the transistor element; and

turning on the transistor element at a predetermined conducting state onthe basis of the second potential difference, generating the lightemission drive current having a current value in accordance with theluminance gradation sequence, and supplying it to the light emissionelement.

According to a fourth aspect of the present invention, there is provideda display unit comprising:

a plurality of display pixels each of which includes a light emissionelement and a light emission drive circuit having an electric chargeaccumulating section for accumulating electric charges based on agradation sequence signal to designate a luminance gradation sequence inaccordance with display data, a light emission control section forgenerating a light emission drive current having a predetermined currentvalue in accordance with the electric charges accumulated in theelectric charge accumulating section and supplying the light emissiondrive current to the light emission element, a writing control sectionfor controlling the supplying state of the electric charges based on thegradation sequence signal to the electric charge accumulating section,and a voltage control section for controlling a drive voltage for makingthe light emission control section perform the operation, respectively;

a selection line in which a writing control signal for controlling theoperation state of the writing control section of the each display pixelis applied;

a hold line in which a voltage control signal for controlling theoperation state of the voltage control section of the each display pixelis applied; and

a data line to which the gradation sequence is supplied.

According to a fifth aspect of the present invention, there is provideda display having:

a selection line;

a hold line;

a data line;

a supplying voltage line;

a hold transistor, in which a gate is connected to the hold line;

a drive transistor having a gate and a current path, the gate of thedrive transistor being connected to one end of a current path of thehold transistor and one end of the current path of the drive transistorbeings connected to the supplying voltage line;

a selection transistor having a gate and a current path, the gate of theselection transistor being connected to the selection line, one end of acurrent path of the selection transistor being connected to the otherend of the current path of the drive transistor, and the other end ofthe current path of the selection transistor being connected to the dataline;

a light emission element which is connected to the other end side of thecurrent path of the drive transistor;

a selection driver which outputs a selection signal to the selectionline;

a hold driver which outputs a hold signal to the hold line;

a data driver which supplies a gradation sequence signal to the dataline; and

a supplying voltage driver which outputs a supplying voltage to thesupplying voltage line.

According to a sixth aspect of the present invention, there is provideda display drive method of a display unit which comprises a display panelmade by a plurality of display pixels and makes the each display pixelperform the light emission operation at a predetermined luminancegradation sequence by supplying a gradation sequence signal designatinga luminance gradation sequence in accordance with the display data tothe each display pixel, and displays desired image information on thedisplay panel, the method comprising:

setting at least part of the plural display pixels at a selection state,and setting a first potential difference equivalent to a thresholdvoltage of the transistor element or a first potential differenceequivalent to the minimum luminance voltage necessary for generating thelight emission drive current required for making the light emissionelement perform the light emission operation at the minimum luminancegradation sequence between one end of a gate and one end of a currentpath of a transistor element for supplying a light emission drivecurrent to a current controlled type of a light emission elementprovided in the each display pixel;

sequentially setting the display pixel for each row of the display panelat a selection state, sequentially applying a gradation sequence signalfor making the light emission element of the each display pixel performthe light emission operation at a predetermined luminance gradationsequence in accordance with the display data, and setting a secondpotential difference in accordance with the luminance gradation sequencebetween a gate and one end of a current path of the transistor element;and

setting at least part of the plural display elements arranged on thedisplay panel at a no-selection state, turning on the transistor elementof the each display element on the basis of the second potentialdifference, and individually generating the light emission drive currenthaving a current value in accordance with the luminance gradationsequence for the each light emission element and supplying the lightemission current to the each light emission element.

The light emission control section may have a drive transistor includinga current path and a control terminal, in which a current value of thelight emission drive current is set due to a potential differencebetween the control terminal and one end of the current path.

The light emission control section may have a drive transistor includinga current path and a control terminal, the drive transistor flowing thelight emission drive current of the current value, which is based on thecurrent value of the writing current flowing through the current path ina light emission operation time period as the gradation sequence signalin a writing operation time period.

The light emission control section may have a drive transistor includinga current path and a control terminal, the drive transistor applying avoltage that attains to a saturated range to one end and the other endof a current path in a light emission operation time period.

A precharge voltage exceeding the threshold of the light emissioncontrol section may be applied to the electric charge accumulatingsection in a period of time of the precharge operation.

The voltage setting section may remain a predetermined electric chargein the light emission control section by partially discharging theelectric charges accumulated in the electric charge accumulating sectionon the basis of the precharge voltage in a period of time of thecorrection operation.

The voltage setting section may further accumulate the electric chargesin accordance with the gradation sequence current in the electric chargeaccumulating section after the period of time of the correctionoperation.

The voltage setting section may be provided with writing control sectionfor controlling the supplying state of the electric charges on the basisof the gradation sequence signal to the electric charge accumulatingsection and voltage control section for controlling the state ofapplying the voltage to the control terminal of the drive transistor.

The voltage setting section may have a precharge voltage applyingsection for applying the precharge exceeding the threshold of the lightemission control section to the electric charge accumulating section andwriting control section for controlling the state of supplying theelectric charges on the basis of the gradation sequence signal to theelectric charge accumulating section. In addition, the precharge voltageand the gradation sequence signal may be selectively applied to theelectric charge accumulating section via the writing control section.

The voltage setting section may have a selection transistor, of whichone end of the current path is connected to one end of the electriccharge accumulating section.

The voltage setting section may have a holding transistor, of which oneend of the current path is connected to the control terminal of thedrive transistor and the other end of the electric charge accumulatingsection.

The voltage setting section may have a selection transistor, of whichone end of the current path is connected to one end of the electriccharge accumulating section and one end of the drive transistor and theother end of the current path is connected to a gradation sequencesignal line through which the gradation sequence signal is flowing and aholding transistor, of which one end of the current path is connected tothe control terminal of the drive transistor and the other end of theelectric charge accumulating section.

The selection transistor may be operated by a first control signal andmay be operated by the second signal that is different from the firstcontrol signal.

According to an eighth aspect of the present invention, there isprovided a drive control method of a light emission drive circuit forflowing a light emission drive current to make a light emission elementto perform light emission, comprising:

a first potential difference step of setting a first potentialdifference on the basis of a precharge voltage that is larger than theminimum luminance gradation sequence necessary for generating the lightemission drive current required for making the light emission element toperform the light emission operation at the minimum luminance gradationsequence or a threshold potential difference between the controlterminal and one end of a current path of the drive transistor in whicha current value of the light emission drive current is set by apotential difference between a control terminal and one end of thecurrent path;

a second potential difference step of setting a second potentialdifference equivalent to the minimum luminance potential difference orthe threshold potential difference between the control terminal and oneend of the current path of the drive transistor by turning on the drivetransistor on the basis of the first potential difference; and

a third potential difference step of setting a third potentialdifference equivalent to the luminance gradation sequence between thecontrol terminal and one end of the current path of the drive transistorby applying a gradation sequence signal for making the light emissionelement to perform the light emission operation at a predeterminedluminance gradation sequence and flowing the gradation sequence signalto the current path of the drive transistor.

The step for setting the third electric potential difference may set thethird electric potential difference by applying the gradation sequencecurrent having a predetermined current value for making the lightemission element to perform the light emission operation at thepredetermined luminance gradation sequence as the gradation sequencesignal to add and accumulate the electric charges based on the gradationsequence current to the electric charges due to the second electricpotential between one the control terminal of the drive transistor andone end of the current path.

According to a ninth aspect of the present invention, there is provideda A display unit comprising:

a light emission element; and

a plurality of display pixels including a light emission drive circuithaving electric charge accumulating section for accumulating electriccharges based on a gradation sequence to designate a luminance gradationsequence in accordance with the display data, light emission controlsection for generating a light emission drive current having apredetermined current value in accordance with the electric chargesaccumulated in the electric charge accumulating section and supplyingthe light emission drive current to the light emission element, andvoltage setting section for partially discharging the electric chargesaccumulated in the electric charge accumulating section in order for thelight emission control section to set the light emission drive currentat the predetermined current value, respectively.

The light emission control section may be provided with a current pathand a control terminal and may have a drive transistor in which acurrent value of a light emission drive current is set due to anelectric potential difference between the control terminal and one endof the current path.

The light emission control section may be provided with a current pathand a control terminal and may have a drive transistor for flowing thelight emission drive current in the light emission operation timeperiod, which is based on the current value of the written currentflowing through the current path as the gradation sequence signal in thewriting operation time period.

The light emission control section may be provided with the current pathand the control terminal and may have a drive transistor in which avoltage saturated in a period of light emission operation is applied toone end and the other end of the current path.

To the electric charge accumulating section, a precharge voltageexceeding the threshold of the drive transistor may be applied in aperiod of time of the precharge operation.

The voltage setting section may remain a predetermined electric chargein the drive transistor by partially discharging the electric chargesaccumulated in the electric charge accumulating section on the basis ofthe precharge voltage in a period of time of the correction operation.

The voltage setting section may remain a predetermined electric chargein the drive transistor by partially discharging the electric chargesaccumulated in the electric charge accumulating section on the basis ofthe precharge voltage in a period of time of the correction operation.

The voltage setting section may further accumulate the electric chargesin accordance with the gradation sequence current in the electric chargeaccumulating section after the period of time of the correctionoperation.

The voltage setting section may have a precharge voltage applyingsection for applying the precharge exceeding the threshold of the drivetransistor to the electric charge accumulating section and writingcontrol section for controlling the state of supplying the electriccharges on the basis of the gradation sequence signal to the electriccharge accumulating section and the precharge voltage and the gradationsequence signal may be selectively applied to the electric chargeaccumulating section via the writing control section.

The voltage setting section may have a selection transistor, of whichone end of the current path is connected to one end of the electriccharge accumulating section.

In the voltage setting section, one end of the current path is connectedto the control terminal of the drive transistor and the other end of theelectric charge accumulating section. A The voltage setting section mayhave a selection transistor, of which one end of the current path isconnected to one end of the electric charge accumulating section and oneend of the drive transistor and the other end of the current path isconnected to a gradation sequence signal line through which thegradation sequence signal is flowing and a holding transistor, of whichone end of the current path is connected to the control terminal of thedrive transistor and the other end of the electric charge accumulatingsection.

The selection transistor may be operated by a first control signal andmay be operated by the second signal that is different from the firstcontrol signal.

The display unit may be provided with gradation sequence signal supplysection for supplying the gradation sequence signal to the each displaypixels via a gradation sequence signal line connected to the voltagesetting section and in the light emission drive circuit of the eachdisplay pixels, the gradation sequence signal applied to the gradationsequence signal line may be applied to the electric charge accumulatingsection via the voltage setting section.

The gradation sequence signal supply section may be provided withsection for generating the precharge voltage exceeding the threshold ofthe light emission control section and applying it to the gradationsequence signal line and in the light emission circuit of the eachdisplay pixel, the precharge voltage applied to the gradation sequencesignal line may be applied to the electric charge accumulating sectionvia the voltage setting section.

The gradation sequence signal supply section may selectively apply theprecharge voltage and the gradation sequence signal to the gradationsequence signal line.

The gradation sequence signal is a gradation sequence current having apredetermined current value for making the light emission element toperform the light emission operation at a desired luminance gradationsequence on the basis of the display data and the electric charges inaccordance with the gradation sequence current may be accumulated in theelectric charge accumulating section.

The voltage setting section may be provided with writing control sectionfor controlling the state of supplying the electric charges to theelectric charge accumulating section based on the gradation sequencesignal and voltage control section for controlling the application stateof the voltage to the control terminal of the drive transistor.

The voltage setting section may be further provided with a writingsignal line in which a writing control signal for controlling theoperational state of the writing control section and a voltage signalline to which a voltage control signal for controlling the operationalstate of the voltage control section of the each display pixel.

The voltage setting section may be further provided with writing drivesection for applying the writing control signal to the writing signalline and voltage drive section for applying the voltage control signalto the voltage signal line.

The voltage setting section may be provided with power source drivesection for applying the supplied voltage to the light emission controlsection.

According to a tenth aspect of the present invention, there is provideda display drive method of a display unit for making light emissionelements of a plurality of display pixels to perform the light emissionarranged in a row direction and a column direction, comprising:

a first potential difference step of setting a first potentialdifference on the basis of a precharge voltage that is larger than theminimum luminance gradation sequence necessary for generating the lightemission drive current required for making the light emission element toperform the light emission operation at the minimum luminance gradationsequence or a threshold potential difference between the controlterminal and one end of a current path of the drive transistor whichsets the display pixel at a selection state and supplies a lightemission drive current to the light emission element;

a second potential difference step of setting a second potentialdifference equivalent to the minimum luminance potential difference orthe threshold potential difference between the control terminal and oneend of the current path of the transistor element by turning on thedrive transistor on the basis of the first potential difference;

a third potential difference step of setting a third potentialdifference equivalent to the luminance gradation sequence between thecontrol terminal and one end of the current path of the drive transistorby applying a gradation sequence signal for making the light emissionelement to perform the light emission operation at a predeterminedluminance gradation sequence and flowing the gradation sequence signalto the current path of the drive transistor; and

a light emission step that the drive transistor flows the light emissiondrive current on the basis of the gradation sequence signal to the lightemission element by applying a voltage so that a potential differencebetween one end and the other end of the current path is saturated tothe other end of the current path of the drive transistor.

The first potential difference step may concurrently set a plurality ofthe display pixels at the selection state. The second potentialdifference step may concurrently set the plural rows of the displaypixels at the no-selection state to set the second potential differenceequivalent to the minimum luminance voltage. The third potentialdifference step may sequentially set the display pixel for each row atthe selection state to sequentially flow the gradation sequence signalto the current path of the drive transistor. The light emission step mayconcurrently flow the light emission drive current to the plural rows ofthe light emission elements.

The step of setting the third potential difference at the each displaypixel may add and accumulate the electric charges based on the gradationsequence current to the electric charges generated by the secondpotential difference to the control terminal of the transistor elementand one end of the current path to set the third potential difference byapplying the gradation sequence current having a predetermined currentvalue for making the light emission element of the each display pixel ata desired luminance gradation sequence as the gradation sequencesignal. * According to an eleventh aspect of the present invention,there is provided a light emission drive circuit, comprising:

light emission control means having a current path of flowing a lightemission drive current from the current path;

electric charge accumulating means for accumulating electric charges inaccordance with a current value of a current flowing through the lightemission control means;

voltage setting means for flowing a current of a current value thatallows the light emission element to perform the light emissionoperation at a predetermined luminance other than the no-light luminancegradation sequence and accumulating the electric charges equivalent tothe predetermined luminance gradation sequence in the electric chargeaccumulating means; and

gradation sequence setting means for discharging the electric chargesequivalent to the predetermined luminance gradation sequence accumulatedin the electric charge accumulating means on the basis of a no-lightluminance gradation sequence signal till this electric charge becomesthe electric charges such that the light emission element equivalent tothe light emission drive current of the current value such that thelight emission element is made into the no-light emission state or theelectric charges such that the light emission drive current does notflow.

The gradation sequence setting means may selectively supply the no-lightemission luminance gradation sequence signal and a gradation sequencesignal equivalent to the luminance gradation sequence other than theno-light emission luminance gradation sequence.

It is preferable that the no-light emission luminance gradation sequencesignal is a voltage signal of a predetermined voltage value and agradation sequence signal equivalent to the luminance gradation sequenceother than the no-light emission luminance gradation sequence is acurrent signal of a predetermined current value.

The gradation sequence setting means may flow a precharge current of anenough current value to make the light emission element to perform thelight emission operation at a higher luminance gradation sequence thanthe predetermined luminance gradation sequence other than the no-lightemission luminance gradation sequence in a period of time of prechargeto the light emission control means so as to accumulate the electriccharges equivalent to the high luminance gradation sequence in theelectric charge accumulating means.

The voltage setting means may flow a correction current of an enoughcurrent value to make the light emission element to perform the lightemission operation at the predetermined luminance gradation sequenceother than the no-light emission luminance gradation sequence in aperiod of time of correction operation to the light emission controlmeans so as to partially discharge the electric charges accumulated inthe electric charge accumulating means.

The light emission control means may be provided with a control terminaland may have a drive transistor in which the current value of the lightemission drive current is set due to the potential difference betweenthe control terminal and one end of the current path.

The light emission control means may be provided with a control terminaland may have a drive transistor to flow the light emission drive currentof the current value in a period of time of the light emissionoperation, which current value is based on the current vale of thewriting current flowing through the current path as the gradationsequence signal in a period of time of the writing operation.

The light emission control means may be provided with a control terminaland may have a drive transistor, in which the voltage arriving at asaturation region is applied to one end of the current path and theother end thereof.

The voltage setting means may be provided with current control meansconnected between one end of the current path of the drive transistorand the gradation sequence setting means for controlling the currentflowing through the current path of the drive transistor and drivetransistor selection control means connected to the control terminal ofthe drive transistor for controlling the selection state of the drivetransistor.

The current control means may have a selection transistor in which acontrol terminal is connected to a selection line and the drivetransistor selection control means may have a holding transistor inwhich a control terminal is connected to a hold line.

The current control means may be operated by the first control signaland the drive transistor selection control means may be operated by thesecond control signal that is different from the first control signal.

According to a twelfth aspect of the present invention, there isprovided a drive control method of a light emission drive circuit forflowing a light emission drive current to make a light emission elementto perform light emission, comprising:

a first potential difference step of generating a first potentialdifference between the control terminal and one end of the current pathof the drive transistor so that, in spite of a luminance gradationsequence signal, the current of the current value to make the lightemission element to perform the light emission operation at apredetermined luminance gradation sequence other than the no-lightemission luminance gradation sequence flows through a current path ofthe drive transistor in advance; and

a second potential difference step of a current value between thecontrol terminal and one end of the current path of the drive transistorgenerating the first potential difference in the first potentialdifference step takes a current value so that the light emission drivecurrent from the drive transistor makes the light emission element intothe no-light emission state on the basis of the no-light emissionluminance gradation sequence signal.

The first potential difference step may flow a precharge current of anenough current value to make the light emission element to perform thelight emission operation at a higher luminance gradation sequence thanthe predetermined luminance gradation sequence other than the no-lightemission luminance gradation sequence in a period of time of prechargeto the current path of the drive transistor and may include a prechargestep to accumulate the electric charges equivalent to the high luminancegradation sequence between the control terminal of the drive transistorand one end of the current path.

The first potential difference step may flow a correction current of anenough current value to make the light emission element to perform thelight emission operation at the luminance gradation sequence lower thanthe higher luminance gradation sequence in a period of time ofcorrection operation to the current path of the drive transistor and mayinclude correction step to partially discharge the electric chargesaccumulated between the control terminal of the drive transistor and oneend of the current path.

According to a thirteenth aspect of the present invention, there isprovided a display unit comprising:

a light emission element; and

a plurality of display pixels comprising a light emission drive circuithaving light emission control means for flowing a light emission drivecurrent from the current path to the light emission element, electriccharge accumulating means for accumulating electric charges inaccordance with the current value of the current flowing the lightemission control means, and voltage setting means for accumulating theelectric charges equivalent to the predetermined luminance gradationsequence in the electric charge accumulating means, respectively; and

gradation sequence setting means for supplying a no-light emissionluminance gradation sequence signal to the display pixel and dischargingthe electric charges equivalent to the predetermined luminance gradationsequence accumulated in the electric charge accumulating means till thelight emission element is made into the electric charges equivalent tothe light emission drive current of the current value such that thelight emission element is made into the no-light emission state or theelectric charges so that the light emission drive current does not flow,wherein the display pixel comprises a light emission element and a lightemission drive circuit, and the light emission drive circuit has thelight emission control means, the electric charge accumulating means,and the voltage setting means. The display unit has the display pixelsand the gradation segment setting means.

The display pixel may be provided with a light emission element and alight emission drive circuit. The light emission drive circuitpreferably has electric charge accumulating means and voltage settingmeans and a display unit has a display pixel and gradation sequencesetting means.

The gradation sequence setting means may electively supply the no-lightemission luminance radation sequence signal and a gradation sequencesignal equivalent to the luminance gradation sequence other than theno-light emission luminance gradation sequence to the display pixel viaa data line.

The no-light emission luminance gradation sequence signal may be avoltage signal of a predetermined voltage value and a gradation sequencesignal equivalent to the luminance gradation sequence other than theno-light emission luminance gradation sequence is a current signal of apredetermined current value.

The gradation sequence setting means may flow a precharge current of anenough current value to make the light emission element to perform thelight emission operation at a higher luminance gradation sequence thanthe predetermined luminance gradation sequence other than the no-lightemission luminance gradation sequence in a period of time of prechargeto the light emission control means so as to accumulate the electriccharges equivalent to the high luminance gradation sequence in theelectric charge accumulating means.

The voltage setting means may flow a correction current of an enoughcurrent value to make the light emission element to perform the lightemission operation at the predetermined luminance gradation sequenceother than the no-light emission luminance gradation sequence in aperiod of time of correction operation to the light emission controlmeans so as to partially discharge the electric charges accumulated inthe electric charge accumulating means.

The light emission control means may be provided with a control terminaland may have a drive transistor in which the current value of the lightemission drive current is set due to the potential difference betweenthe control terminal and one end of the current path.

The light emission control means may be provided with a control terminaland may have a drive transistor to flow the light emission drive currentof the current value in a period of time of the light emissionoperation, which current value is based on the current vale of thewriting current flowing through the current path as the gradationsequence signal in a period of time of the writing operation.

The light emission control means may be provided with a control terminaland may have a drive transistor, in which the voltage arriving at asaturation region is applied to one end of the current path and theother end thereof.

The voltage setting means may be provided with current control meansconnected between one end of the current path of the drive transistorand the gradation sequence setting means for controlling the currentflowing through the current path of the drive transistor and drivetransistor selection control means connected to the control terminal ofthe drive transistor for controlling the selection state of the drivetransistor.

The current control means may have a selection transistor in which acontrol terminal is connected to a selection line and the drivetransistor selection control means may have a holding transistor inwhich a control terminal is connected to a hold line.

The current control means may be provided with a selection driver foroutputting the selection signal to the current control means via theselection line and a holding driver for outputting the hold signal tothe drive transistor selection means via the hold line.

The selection signal and the hold signal may be different from eachother.

A supply voltage driver for supplying the supplying voltage to the otherend of the current path of the light emission control means via a supplyvoltage line may be further provided.

The gradation sequence setting means may output a precharge voltage toflow the precharge current of an enough current value to make the lightemission element to perform the light emission operation at a higherluminance gradation sequence than the predetermined luminance gradationsequence other than the no-light emission luminance gradation sequenceto the current path of the light emission control means via a data line.

According to a fourteenth aspect of the present invention, there isprovided a display drive method of a display unit for making lightemission elements of a plurality of display pixels to perform the lightemission arranged in a row direction and a column direction, comprising:

a first potential difference step of generating a first potentialdifference between the control terminal and one end of the current pathof the drive transistor so that, in spite of a luminance gradationsequence signal, the current of the current value to make the lightemission element of the display pixel to perform the light emissionoperation at a predetermined luminance gradation sequence other than theno-light emission luminance gradation sequence flows through a currentpath of the drive transistor in advance; and

a second potential difference step of a current value between thecontrol terminal and one end of the current path of the drive transistorgenerating the first potential difference in the first potentialdifference step takes a current value so that the light emission drivecurrent from the drive transistor makes the light emission element intothe no-light emission state on the basis of the no-light emissionluminance gradation sequence signal.

The first potential difference step may flow a precharge current of anenough current value to make the light emission element to perform thelight emission operation at a higher luminance gradation sequence thanthe predetermined luminance gradation sequence other than the no-lightemission luminance gradation sequence in a period of time of prechargeto the current path of the drive transistor and may include a prechargestep to accumulate the electric charges equivalent to the high luminancegradation sequence between the control terminal of the drive transistorand one end of the current path.

The first potential difference step may flow a correction current of anenough current value to make the light emission element to perform thelight emission operation at the luminance gradation sequence lower thanthe higher luminance gradation sequence in a period of time ofcorrection operation to the current path of the drive transistor and mayinclude correction step to partially discharge the electric chargesaccumulated between the control terminal of the drive transistor and oneend of the current path.

The precharge step may concurrently set a plurality of the displaypixels at the selection state, the correction step may concurrently setthe plural rows of the display pixels at the no-selection state to setthe first potential difference equivalent to the low luminance voltage.

The second potential difference step may sequentially flow the no-lightemission luminance gradation sequence signal of a predetermined voltagevalue to the current path of the drive transistor of the display pixelto be made into a no-light emission state.

The second potential difference step may sequentially flow the luminancegradation sequence signal of a predetermined current value to thecurrent path of the drive transistor of the display pixel to be madeinto a light emission state.

According to the present invention, it is possible to set the writingcontrol means and the voltage control means at the state such that thelight emission control means can flow the light drive current withoutdelay.

According to the light emission drive circuit of the present invention,by controlling the selection transistor and the hold transistorrespectively, it is possible to set the drive transistor so as to flowthe light emission drive current without delay.

According to the drive control method of the light emission drivecircuit, the light emission drive circuit is set at the thresholdvoltage of the transistor element or the voltage equivalent to theminimum luminance gradation sequence necessary for generating the lightemission drive current when making the light emission element to performthe light emission operation at the minimum luminance gradation sequencein the step of setting the first potential difference in advance.Therefore, it is possible to easily set the light emission drive circuitat the appropriate luminance gradation sequence in accordance with thedisplay data.

According to the display unit of the present invention, it is possibleto set the writing control means and the voltage control means at thestate such that the light emission control means can flow the lightdrive current without delay.

According to the display unit of the present invention, it is possibleto set the drive transistor so as to flow the light emission drivecurrent without delay by controlling the selection transistor and thehold transistor respectively.

According to the drive control method of the 1 the display unit of thepresent invention, the light emission drive circuit is set at thethreshold voltage of the transistor element or the voltage equivalent tothe minimum luminance gradation sequence necessary for generating thelight emission drive current when making the light emission element toperform the light emission operation at the minimum luminance gradationsequence in the step of setting the first potential difference inadvance. Therefore, it is possible to easily set the light emissiondrive circuit at the appropriate luminance gradation sequence inaccordance with the display data.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

FIG. 1 is a circuit block diagram showing an embodiment of a lightemission drive circuit according to the invention;

FIG. 2 is a timing chart showing a first example of the drive controloperation of the light emission drive circuit according to theembodiment;

FIGS. 3A and 3B are conceptual drawings showing the operation examples(precharge operation/threshold correction operation) of the lightemission drive circuit according to the embodiment in the differentstate;

FIGS. 4A and 4B are conceptual drawings showing the operation examples(writing operation/light emission operation) of the light emission drivecircuit according to the embodiment in the different state;

FIG. 5 is a graph showing a current property and a voltage property ofthe light emission drive circuit according to the embodiment;

FIG. 6 is a graph showing a temporal response of a voltage between agate and a source of a thin film transistor in a time of period of athreshold correction operation;

FIG. 7 is a graph showing a temporal response of a voltage between adrain and a source of a thin film transistor in a time of period of athreshold correction operation;

FIG. 8 is a graph showing a changing trend of a light emission drivecurrent against a gradation sequence current in a contrast example witha drive control method of the light emission drive circuit according tothe embodiment;

FIGS. 9A and 9B are graphs showing a changing trend of an outputgradation sequence against an input gradation sequence in the drivecontrol method of the light emission drive circuit according to theembodiment in the case of different threshold voltages of a drivetransistor;

FIG. 10 is a timing chart showing a second example of the drive controloperation of the light emission drive circuit according to theembodiment;

FIGS. 11A and 11B are conceptual views showing the operation example(precharge operation/voltage correction operation) of the light emissiondrive circuit according to the embodiment in the different state;

FIGS. 12A and 12B are conceptual views showing the operation example(writing operation/light emission operation) of the light emission drivecircuit according to the embodiment in the different state;

FIG. 13 is a timing chart showing a third example of the drive controloperation of the light emission drive circuit according to theembodiment;

FIGS. 14A and 14B are conceptual views showing the operation example(writing operation/light emission operation) of the light emission drivecircuit according to the embodiment in the different state;

FIG. 15 is a schematic block diagram showing an example of the entirestructure of a display unit according to the embodiment;

FIG. 16 is a schematic block diagram showing a display panel to beapplied to the display unit according to the embodiment and an exampleof its peripheral circuit;

FIG. 17 is a schematic block diagram showing an example of a data driverthat can be applied to the display unit according to the embodiment;

FIG. 18 is a schematic block diagram showing an example of a gradationsequence signal generating section that can be applied to the datadriver according to the embodiment;

FIG. 19 is a schematic block diagram showing the structures ofsubstantial parts of a gradation sequence signal generating section thatcan be applied to the data driver according to the embodiment;

FIG. 20 is a timing chart showing an example of a isplay drive method ofthe display unit according to the embodiment;

FIG. 21 is a circuit block diagram showing the other light emissiondrive circuit according to the embodiment;

FIG. 22 is a schematic block diagram showing the substantial parts of alight emission element type of a display according to a prior art; and

FIG. 23 is an equivalent circuit diagram showing a constituent exampleof a light emission element (a light emission circuit and a lightemission terminal) type of a display according to the prior art.

DETAILED DESCRIPTION OF THE INVENTION

An emission drive circuit and its drive control method and a displayunit and its display drive method according to the invention will bedescribed in detail below with reference to the embodiment. <Lightemission drive circuit>First, the emission drive circuit and its drivecontrol method according to the invention will be described withreference to the drawings below.

FIG. 1 is a circuit block diagram showing an embodiment of a lightemission drive circuit according to the invention.

As shown in FIG. 1, for example, a light emission drive circuit DCaccording to the invention is configured so as to have: a selectiontransistor (writing control means) Tr 12 configured by a thin filmtransistor located in the vicinity of each intersecting point of aplurality of selection lines SL and a plurality of data lines DLarranged so as to be at right angles to each other, in which a gateterminal (a control terminal) is connected to a selection line SL and asource terminal and a drain terminal (one end and the other end of acurrent path) are connected to the data line DL and a contact point N12,respectively; a holding transistor (voltage control means) Tr 11configured by a thin film transistor, in which a gate terminal isconnected to a hold line HL arranged in parallel with the selection lineSL, and a drain terminal and a source terminal are connected to asupplying voltage line VL to which a supplying voltage Vsc is outputtedand a contact point Nil, respectively;

a drive transistor (light emission control means) Tr 13 configured by athin film transistor in which a gate terminal is connected to thecontact point Nil, a drain terminal is connected to a supplying voltageline VL, and a source terminal is connected to a contact point N12,respectively; and a capacitor (electric charge accumulating means and acapacity element) Cs connected between the contact point N11 and thecontact point N12 (namely, between the gate terminal and the sourceterminal of the drive transistor Tr 13). In an organic EL element (acurrent control type of a light emission element) OEL, an anode terminalis connected to the contact point N12 of the light emission drivecircuit DC and a common voltage Vcom is applied to a cathode terminal.The common voltage Vcom is set at a potential equal to that of aselection voltage value Vs that is the supplying voltage Vsc in a timeof period of the writing operation Twr (to be described later) or apotential higher than the selection voltage value Vs. Further, thecommon voltage Vcom is set at a lower potential than that of a lightemission voltage value Ve that is the supplying voltage value Vsc in atime of period of the light emission operation Tem (to be describedlater).

Here, the capacitor Cs may be a parasitic capacitance formed between agate and a source of the drive transistor Tr 13 or it may be made byfurther connecting a capacitance element between the contact point N11and the contact point N12 in parallel in addition to the parasiticcapacitance. In addition, the transistors Tr 11 to Tr 13 are notparticularly limited. However, an n channel type of amorphous siliconTFT can be applied by composing the all of the transistors Tr 11 to Tr13 by an n channel type of a thin firm transistor. In this case, byapplying an amorphous silicon manufacturing technology that has beenalready established, it is possible to manufacture a light emissiondrive circuit of which operational property is stable, in a relativelyeasy manufacturing process. In addition, a light emission element ofwhich light emission is driven by a light emission drive circuit DC isnot limited to the organic EL element OEL shown in FIG. 1. The lightemission element may be other light emission element such as a lightemission diode if it is a current control type of a light emissionelement.

In other words, the light emission drive circuit DC according to theembodiment is configured in such a manner that, on the basis of a signallevel of a control signal (a hold signal and a selection signal to bedescribed later) to be applied to the hold line HL and the selectionline SL individually, the hold transistor Tr 11 and the selectiontransistor Tr 12 are operated individually being turned on and off.

As shown in FIG. 1, the light emission drive circuit DC according to theembodiment is configured with a signal drive circuit SDR connected tothe data line DL, which signal drive circuit SDR is provided with meansfor selectively supplying any of a gradation sequence current Idata thatthe organic EL element OEL emits the light at a desired luminancegradation sequence or a no-light emission display voltage (a gradationsequence voltage) Vzero that the organic EL element OEL does not emit alight and becomes the darkest display (a black display) to the lightemission drive circuit DC as a gradation sequence signal for making theorganic EL element OEL to perform the light emission operation at aluminance gradation sequence and means for supplying a precharge voltageVpre of which potential is sufficiently lower than a selection voltagevalue Vs at a period of time of the writing operation Twr to the lightemission drive circuit DC as a control voltage for correcting an elementproperty (a threshold voltage property) of the above-described drivetransistor Tr 13 before the operation of writing the gradation sequencesignal. Here, as described in a drive control method to be describedlater, the signal drive circuit SDR is provided with switch means SMthat is switch-controlled so that the gradation sequence signal of thegradation sequence current Idata or the no-light emission displayvoltage Vzero is supplied to the data line DL at a period of time of thewriting operation Twr and the precharge voltage Vpre is supplied to thedata line DL at a period of time of the precharge operation Tpre to bedescribed later.

<Drive control method of light emission drive circuit

(Gradation display: (1))

Next, a first example of a drive control method of the light emissiondrive circuit having the above-described structure (the gradationsequence display operation) will be described below.

FIG. 2 is a timing chart showing a current value of the data line DL, apotential of a selection signal Ssel, a potential of a hold signal Shld,a potential of a supplying voltage Vsc, a potential difference betweenthe opposite ends of a capacitor Cs, and a current value of a lightemission drive current Iem flowing through the organic EL element OEL.FIGS. 3A and 3B are conceptual drawings showing the operation examples(precharge operation/threshold correction operation) of the lightemission drive circuit according to the embodiment. FIGS. 4A and 4B areconceptual drawings showing the operation examples (writingoperation/light emission operation) of the light emission drive circuitaccording to the embodiment.

As shown in FIG. 2, the drive control operation of the light emissiondrive circuit according to the embodiment is carried out by setting thelight emission drive circuit so as to include a precharge operation timeperiod Tpre of accumulating a predetermined electric charge in thecapacitor Cs of the light emission drive circuit DC, a thresholdcorrection operation time period Tth of partially discharging theelectric charges accumulated in the capacitor Cs of the light emissiondrive circuit DC in the precharge operation time period Tpre andremaining the electric charges equivalent to the threshold of thedrain-to-source current Ids of the drive transistor Tr 13 in thecapacitor Cs and holding the electric charges, a writing operation timeperiod Twr of applying the gradation sequence signal in accordance withthe display data via the data line DL and writing the electric chargesin accordance with the display data in the capacitor Cs, and a lightemission operation time period Tem of making the organic EL element toperform the light emission operation at the luminance gradation sequencein accordance with the display data on the basis of the electric chargesaccumulated in the capacitor Cs so that a predetermined prechargevoltage Vpre is applied from the signal drive circuit SDR via the dataline DL within one processing cycle Tcyc to acquire a gate-to-sourcevoltage Vpre13 of the drive transistor Tr 13 (the absolute value of thevoltage Vpre13 is larger than the absolute value of a gate-to-sourcevoltage Vth13 of the drive transistor Tr 13. In an n channel transistor,the voltage Vpre13 is higher than the threshold voltage Vth13)(Tcyc≧Tpre+Tth+Twr+Tem).

Here, the threshold voltage of the above-described drain-to-sourcecurrent Ids of the drive transistor Tr 13 is a gate-to-source voltage ofthe drive transistor Tr 13 of a border line between the case that thedrain-to-source current Ids of the drive transistor Tr 13 starts to flowand the case the drain-to-source current Ids of the drive transistor Tr13 does not start to flow. In addition, the one processing cycle Tcyc isa time period required in order for a display pixel EM to display theimage for one pixel in the image of one frame. In the case of displayingthe image of one frame by arranging a plurality of display pixels EM ina matrix in row and column directions to display the image for oneframe, the one processing cycle Tcyc is a time period required in orderfor the display pixel EM for one row displays the image for one row inthe image for one frame. The precharge operation time periods Tpre andthe threshold correction operation time periods Tth may be acquired atthe same time in plural rows and the light emission operation timeperiods Tem may be acquired at the same time in plural rows whiledeviating the writing operation time period Twr to write the data foreach row.

The above-described each operation time period will be described indetail below. (Precharge operation time period) First, in the prechargeoperation time period Tpre, as shown in FIGS. 2 and 3A, the selectionsignal (the writing control signal) Ssel of the on level (a high levelwhen the hold transistors Tr 11 and Tr 12 are the n-channel type of thethin film transistors) and the hold signal (the voltage control signal)Shld are applied to the selection line SL and the hold line HL, and thesupplying voltage Vsc of the lower potential selection voltage value Vsis applied to the supplying voltage line VL of the light emission drivecircuit DC. The selection voltage value Vs may be a voltage not morethan the common voltage Vcom, for example, it may be a ground potential.Further, in synchronization with this timing, the switch means SM of thesignal drive circuit SDR outputs the precharge voltage Vpre to the dataline DL.

FIG. 5 is a graph showing a drain-to-source current Ids property whenmodulating the drain-to-source voltage Vds at a predeterminedgate-to-source voltage Vgs in the n channel type of the thin filmtransistor. Here, if the thin film transistor is replaced with the drivetransistor Tr 13, a horizontal axis can represent a partial pressure ofthe organic EL element OEL and a partial pressure of the organic ELelement OEL that is connected in series with the drive transistor Tr 13and a horizontal axis can represent a current value of the current Idsbetween the drain and the source of the drive transistor Tr 13. In thedrawing, a dashed line represents a border line of the gate-to-sourcethreshold voltage of the drive transistor Tr 13. In this case, the leftside of the border line represents an unsaturated range and the rightside represents a saturation range. A solid line represents a propertyof a drain-to-source current Ids when the drain-to-source voltage Vds ofthe thin film transistor is modulated while fixing the gate-to-sourcevoltage Vgs of the thin film transistor to a voltage Vgsmax of themaximum luminance modulation, Vgsl (<Vgsmax) and Vgs2 (<Vgsl),respectively. A broken line is an EL load line when the thin filmtransistor is replaced with the drive transistor Tr 13. The voltage atthe right side of the EL load line becomes the partial pressure of theorganic EL element OEL at the supplying voltage Vsc-to-common voltageVcom voltage (in the drawing, 20V), and the left side of the EL loadline is equivalent to the drain-to-source voltage Vds of the drivetransistor Tr 13. The more the current value of the drain-to-sourcecurrent Ids (namely, the gradation sequence current Idata) of the drivetransistor Tr 13 is increased, the more this partial pressure of theorganic EL element OEL is increased little by little.

In the unsaturated range, assuming that the gate-to-source voltage Vgsof the drive transistor Tr 13 is fixed, the more the drain-to-sourcevoltage Vds of the drive transistor Tr 13 is increased, the more thecurrent value of the drain-to-source voltage Ids is increased. On theother hand, in the saturation range, assuming that the gate-to-sourcevoltage Vgs of the drive transistor Tr 13 is fixed, even if thedrain-to-source voltage Vds is increased, the drain-to-source currentIDS of the drive transistor Tr 13 is not increased so much and is nearlyfixed.

The precharge voltage Vpre to be also applied between the drain and thesource of the drive transistor Tr 13 in the precharge operation timeperiod Tpre is sufficiently lower than the selection voltage value Vs inthe writing operation time period Twr. In addition, the prechargevoltage Vpre is set at a potential such that the gate-to-source voltageVgs of the drive transistor Tr 13 arrives at the saturation of thetransistor shown in FIG. 5, namely, the drain-to-source voltage Vds ofthe drive transistor Tr 13 arrives at the saturation range.

If the hold signal Shld at an on level is outputted from the hold lineHL, the holding transistor Tr 11 provided in the light emission drivecircuit DC composing the display pixel EM is turned on and the supplyingvoltage Vsc is applied to the gate of the drive transistor Tr 13 and oneend (the contact point Nll) of the capacity Cs via the hold transistorTr 11. The selection signal Ssel of the on level is outputted from theselection line SL. Consequently, the selection transistor Tr 12 isturned on and the data line DL to which the precharge voltage Vpre isapplied electrically communicates with the source of the drivetransistor Tr 13 and the other end of the capacitor Cs (the contactpoint N12) via the selection transistor Tr 12.

Here, the precharge voltage Vpre to be applied to the data line DL fromthe signal drive circuit SDR in the precharge operation time period Tpreis set so as to meet the following equation (1):|Vs−Vprel|>Vth12+Vth13   . . . (1)wherein Vthl2 is a drain-to-source threshold voltage of the selectiontransistor Tr 12 when the on-level selection signal Ssel is applied tothe gate of the selection transistor Tr 12. In addition, since both ofthe gate and the drain of the drive transistor 13 are applied with theselection voltage value Vs-in the precharge operation time period Tpre,they have the substantially same potentials. Accordingly, Vth13 is adrain-to-source voltage threshold voltage of the transistor Tr 13 and isalso a gate-to-source threshold voltage of the drive transistor Tr 13.In the meantime, Vth12+Vth13 are increased with time and it has apotential difference of Vs - Vpre so as to always meet the equation (1).

Thus, the potential difference Vpre13 that is larger than the thresholdVth13 of the drive transistor Tr 13 is applied to the opposite ends ofthe capacitor Cs (namely, between the gate and the source of the drivetransistor Tr 13). Thereby, the precharge current Ipre of the largecurrent in accordance with this drive transistor precharge voltageVpre13 compulsorily flows from the supplying voltage line VL toward thesignal drive circuit SDR between the drain and the source of the drivetransistor Tr 13. Accordingly, the electric charges corresponding to thepotential difference Vc in accordance with the precharge current Ipre isaccumulated without delay at the opposite ends of the capacitor Cs(namely, the drive transistor precharge voltage Vpre13 (the thirdpotential difference) is charged). In the meantime, in the prechargeoperation time period, not only the electric charges is accumulated inthe capacitor Cs but also the electric charges is accumulated so thatthe precharge current Ipre flows also in the other capacitance of thecurrent route from the supplying voltage line VL till the data line DL.

In this case, the common voltage Vcom not more than the low potentialsupplying voltage Vsc (=Vs) is applied to the cathode terminal of theorganic EL element OEL. For this reason, the state between an anode anda cathode of the organic EL element OEL is set at an inverse biasedstate or a no-electric field state, so that the light emission drivecurrent does not flow through the organic EL element and the lightemission operation is not carried out. (Threshold correction operationtime period) Next, in the threshold correction operation time period Tthafter the precharge operation time period Tpre is terminated, as shownin FIGS. 2 and 3B, the selection signal Ssel applied to the selectionline SL is changed into an off level (a low level) with the on levelhold signal Shld applied to the hold line HL, whereby the holdtransistor Tr 11 may hold the on state and the selection transistor Tr12 is turned off. Thereby, the other end of the capacitor Cs (thecontact point N12) is electrically separated from the data line DL to beset at a high impedance state.

In this case, the drive transistor Tr 13 is kept at the on state by theelectric charges (the opposite end's potential Vc>Vth13) accumulated inthe capacitor CS in the above-described precharge operation time periodTpre. Therefore, the current may flow between the drain and the sourceof the drive transistor Tr 13 as the gate voltage of the drivetransistor Tr 13 is held. Consequently, the potential at the sourceterminal side of the drive transistor Tr 13 (the contact point N12; theother terminal side of the capacitor Cs) is gradually increased so as toapproach the drain terminal side (the supplying voltage line VL side).

Thereby, as shown in FIG. 6, the gate-to-source voltage Vgs of the drivetransistor Tr 13 is decreased, the electric charges accumulated in thecapacitor C13 is partially discharged, and finally, the gate-to-sourcevoltage Vgs of the drive transistor Tr 13 is changed so as to decrease(=converge) to the threshold voltage Vth13 (the first potentialdifference) of the drive transistor Tr 13. In addition, as shown in FIG.7, the drain-to-source current Ids of the drive transistor Tr 13 isdecreased and finally, the drain-to-source current Ids is changed so asto have a linearity.

FIG. 6 is a graph showing a temporal response of a voltage between agate and a source of a thin film transistor in a time of period of athreshold correction operation according to the present embodiment. FIG.7 is a graph showing a temporal response of a current between a drainand a source of a thin film transistor in a time of period of athreshold correction operation according to the present embodiment.

In these results, applying the light emission drive circuit DC having anelement structure and an element property as shown in Table 1, atemporal response of a gate-to-source voltage Vgs of the drivetransistor Tr 13 and a temporal response of the drain-to-source currentIds in the case where a potential difference |Vs−Vpre| is set at 10V and6.5V are observed to be shown using a logarithmic scale. In themeantime, the capacitance Ct is a sum of the capacity of the capacitorCs and the other parasitic capacity generated in the light emissiondrive circuit DC. TABLE 1 (Structure or light emission drive circuit DC)Gate capacity Cin of Drive transistor Tr 13 1.62E−01fF/μm² Gate width Wof Drive transistor Tr 13 1200 μm Gate length L of Drive transistor Tr13 7 μm Potential difference |Vs − Vpre| 10 V/6.5 V Threshold voltageVth13 of drive 1.5 V transistor Tr 13 Capacity Ct 20 pF Number ofgradation sequence 256 Maximum luminance gradation sequence 6.53 Vvoltage Vmsb Light emission current in maximum 1.20E−05A/dot(MSB)luminance gradation sequence Light emission current in minimum4.68E−08A/dot(LSB) luminance gradation sequence

In FIGS. 6 and 7, Spa is a property line representing a changing trendof the gate-to-source voltage Vgs in the case where the above-describedpotential difference |Vs−Vpre|is set at 10V and SPb is a property linerepresenting a changing trend of the gate-to-source voltage Vgs in thecase where the potential difference |Vs−Vpre| is set at 6.5V. Thepotential difference 3.5V of 10V and 6.5V assumes changing with time ofa partial pressure between the gate and the source of the drivetransistor Tr 13 in accordance with temporal change of increase anddecrease such as the drive transistor Tr 13 and the selection transistorTr 12. In addition, Vmsb is a gate-to-source voltage Vgs of the drivetransistor Tr 13 when the organic EL element OEL is made to perform thelight emission operation at the maximum luminance gradation sequence(MSB). Imsb is a drain-to-source current Ids (the light emission drivecurrent Iem) of the drive transistor Tr 13. Ilsb is a drain-to-sourcecurrent Ids (the light emission drive current Iem) of the drivetransistor Tr 13 when the organic EL element OEL is made to perform thelight emission operation at the minimum luminance gradation sequence(LSB) in the gradation sequences except for the no-light emission.

In this case, in the thin film transistor shown in the table 1, as shownin FIG. 6, it is proved that, in spite of the potential difference|vs−Vpre| generated in the above-described precharge operation timeperiod Tpre, the gate-to-source voltage Vgs (the opposite ends'potential Vc of the capacitor Cs) decreases into a threshold voltagevalue Vth13 (=1.5V) in a passage of time about 3 msec to 4 μsec (3000μsec to 4000 μsec). Further, as shown in FIG. 7, it is proved that, inspite of the potential difference |vs - Vpre| generated in theabove-described precharge operation time period Tpre, thedrain-to-source voltage Ids is decreased to a current value 4.68E-8A (inthe graph of FIG. 6, the gate-to-source voltage Vgs is decreased aboutto 2.0V) in a passage of time about 50 μsec to 200 μsec.

In this threshold correction operation time period Tth, since thepotential of the anode terminal (the contact point N12) of the organicEL element OEL is the same as the common voltage Vcom at the cardterminal side or has the potential less than the common voltage Vcom atthe card terminal side, the no-potential or the inverse biased voltagehas been applied yet to the organic EL element OEL and the organic ELelement OEL does not perform the light emission operation. (Writingoperation time period) Next, in the writing operation time period Twrafter the threshold correction operation time period Tth is terminated,process is executed as shown in FIGS. 2 and 4A. That is, in the casewhere the selection line SL is applied to the on line selection signalSsel again continuously keeping the hold signal Shld at the on level andthe display pixel EM is a gradation sequence display other than theno-light emission in synchronization with this timing, the switchingmeans SM of the signal drive circuit SDR may set the gradation sequencecurrent Idata along an arrow direction in accordance with the displaydata so as to flow from the supplying voltage line VL into the signaldrive circuit SDR via the data line. In addition, in the case where thedisplay pixel EM is the gradation sequence display of the no-lightemission, the switching means SM of the signal drive circuit SDR mayoutput the no-light emission display voltage Vzero in which thegate-to-source voltage of the drive transistor Tr 13 is made not morethan the threshold value to the data line DL.

In this case, the normal gradation sequence display operation (thegradation sequence display for making the organic EL element OEL toperform the light emission operation) will be described and the no-lightemission operation (the gradation sequence display operation so as notto make the organic EL element OEL to perform the light emissionoperation) will be described later.

Thereby, when the selection transistor Tr 12 is turned on and theoperation to drain the gradation sequence current Idata via the dataline DL is carried out, the voltage of the potential further lower thanthe low voltage of the supplying voltage Vsc (=Vs) is applied to thecontact point N12 (the source terminal of the drive transistor Tr 13 andthe other end side of the capacitor Cs). In the meantime, to one endside (the contact point Nll) of the capacitor Cs, the low potentialsupplying voltage Vsc (=Vs) of the supplying voltage line VL is appliedvia the hold transistor Tr 11.

Here, the most voltage components among the gate-to-source voltages ofthe drive transistor Tr 13 required for flowing the gradation sequencecurrent Idata between the drain and the source of the drive transistorTr 13 are the threshold voltage Vth13. In particularly, in the lowestluminance voltage Vlsb, the ratio of the electric charges needed by thethreshold voltage Vth13 in the all electric charges exceeds 50%. Tryingto charge the electric charges to arrive at this threshold voltage Mth13only by the writing operation without the precharge operation and thethreshold correction operation according to the embodiment, namely, bythe current of which current value is small about the gradation sequencecurrent Idata, the writing operation time period Twr is made longer.Therefore, a frame period to display one image is made longer, so that agood display property is lost. However, according to the presentembodiment, in the capacitor Cs connected to the contact point Nll andthe contact point N12 (between the gate and the source of the drivetransistor Tr 13), the electric charges equivalent to the thresholdvoltage Vth13 of the drive transistor Tr 13 is held (the thresholdvoltage Vth13 is charged) by the above-described precharge operation andthe threshold correction operation. Therefore, it is possible to chargethe electric charges required for making the gradation sequence currentIdata steady between the drain and the source of the drive transistor Tr13 even by the minute current about the gradation sequence current Idatain a relatively short time.

Thus, the drive transistor Tr 13 is set so as to arrive at the drivetransistor precharge voltage Vpre 13 higher than the threshold voltageVth13 (namely, the absolute value thereof is larger that of thethreshold voltage Vth13) compulsorily and without delay by outputtingthe precharge voltage Vpre, which is not a minute current and meets theequation (1) and the gate-to-source voltage of the drive transistor Tr13 is controlled to cognate into the threshold voltage Vth13 in thethreshold correction operation time period Tth. Consequently, as shownin FIG. 4A, the writing current Ia in accordance with the current valueof the gradation sequence current Idata flows to the signal drivecircuit SDR without delay from the supplying voltage line VL via thedrive transistor Tr 13, the contact point N12, the selection transistorTr 12, and the data line DL.

In other words, as shown in FIG. 6, the electric charges equivalent tothe threshold voltage Vth13 of the drive transistor Tr 13 is accumulatedin the threshold correction operation time period Tth in the capacitorCs. For this reason, it is enough that the electric charges needed bythe voltage component Vdata in accordance with the gradation sequencecurrent Idata (the writing current Ia) is charged in addition to thecharging state. Even if the threshold voltage Vth13 of the drivetransistor Tr 13 is changed due to a light emission history and anelement property or the like, it is possible to write the voltagecomponent Vdata appropriately in accordance with the gradation sequencesignal (the display data) sufficiently without delay. Here, the voltageVc to be charged in the capacitor Cs (=Vα; the second potentialdifference) is made into a sum Vα=Vth13+Vdata of the voltage componentVdata in accordance with the threshold voltage Vh13 and the gradationsequence current Idata.

In this case, the low potential supplying voltage Vsc (=Vs) is appliedto the supplying voltage line VL and further, the writing current Ia iscontrolled to flow in a data line DL direction from the supplyingvoltage lien via the light emission drive circuit DC. Consequently, thepotential to be applied to the anode terminal (the contact point N12) ofthe organic EL element OEL is made not more than the potential Vcom ofthe cathode terminal and the inverse biased voltage is applied to theorganic EL element OEL. Therefore, the light emission drive current doesnot flow through the organic EL element OEL and the light emissionoperation is not carried out. (Light emission operation time period)Next, in the light emission operation Tem after the writing operationtime period Twr is terminated, as shown in FIGS. 2 and 4B, the off levelselection signal Ssel and the hold signal Shld are together applied tothe selection line SL and the hold line HL. In synchronization with thistiming, the drawing operation of the gradation sequence current Idatadue to the signal drive circuit SDR is stopped and the voltage value Venot less than the anode voltage needed when making the organic ELelement OEL to perform the light emission operation at the maximumluminance gradation sequence (the positive voltage that is an order biaswith respect to the voltage Vcom connected to the cathode side of theorganic EL element OEL) is applied to the supplying voltage line VL asthe high potential supplying voltage Vsc. The light emission voltagevalue Ve is a higher potential than the selection voltage value Vs.

Specifically, the light emission voltage value Ve is set at a potentialto meet the following equation (2):|Ve−Vcom|>Vdsmax+Velmax   . . . (2)wherein, Vdsmax is the maximum current value between the drain and thesource of the drive transistor Tr 13 that the voltage between the drainand the source of the drive transistor Tr 13 arrives at the saturationrange shown in FIG. 5 in the light emission operation time period Temwhen flowing the gradation sequence current Idata at the maximumluminance gradation sequence. As a result, the drain-to-source currentof the drive transistor Tr 13 (the gradation sequence current Idata) canbe uniquely set by the gate-to-source voltage of the drive transistor Tr13. In other words, the gate-to-drain voltage of the drive transistor Tr13, namely, the electric charges amount accumulated in the capacitor C3can be uniquely set by the drain-to-source voltage of the drivetransistor Tr 13 (the gradation sequence current Idata). Velmax is apartial pressure of the organic EL element OEL at the maximum luminancegradation sequence.

Since the drain-to-source voltage of the drive transistor Tr 13 islocated in the saturation range in the light emission operation timeperiod Tem of the drive transistor Tr 13, Vds is set at a voltage tomeet the following equation (3).|Ve−Vcom|>Vds ≧Vth13   . . . (3)

In other words, if the drain-to-source voltage Vds of the drivetransistor Tr 13 is lower than the threshold Vth13 in the light emissionoperation time period Tem without meeting the equation (3), it is notpossible to uniquely set the drain-to-source current Ids of the drivetransistor Tr 13 by the gate-to-source voltage of the drive transistorTr 13.

If IVe - Vcoml is constant, the more the luminance gradation sequence isheightened, the more |Vds−Vth| is decreased. In other words, if Vdsmaxmeets the following equation (4), at any gradation sequence, thedrain-to-source voltage of the drive transistor Tr 13 is always locatedin the saturation range in the light emission operation time period Tem.|Ve−Vcom|>Vdsmax ≧Vth13max   . . . (4)

In the meantime, in FIG. 5, Ve−Vcom is defined as 20V, and however, thepresent embodiment is not limited to this.

The holding transistor Tr 11 and the selection transistor Tr 12 providedto the light emission drive circuit DC are turned off, and the capacitorCs holds the electric charges accumulated in the above-described writingoperation time period Twr.

Thus, since the capacitor Cs holds the charging voltage Va upon thewriting operation (=Vth13+Vdata), the gate-to-source voltage Vgs of thedrive transistor Tr 13 (the voltage of the contact point N11; the drivevoltage) is held and the drive transistor Tr 13 is kept to be turned on.

Accordingly, as shown in FIG. 4B, in the light emission operation timeperiod Tem, the light emission drive current Iem flows in the directionof the organic EL element OEL from the supplying voltage line VL via thedrive transistor Tr 13 and the contact point N12 and the organic ELelement OEL emits light at a predetermined luminance gradation sequencein accordance with the current value of the light emission drive currentIem. Here, the electric charges held in the capacitor Cs in the lightemission operation time period Tem (namely, the charging voltage Vc) isequivalent to the potential difference in the case of flowing thewriting current Ia corresponding to the gradation sequence current Idatain the drive transistor Tr 13. For this reason, the light emission drivecurrent Iem flowing through the organic EL element OEL has the currentvalue (Iem nearly equal to Ia =Idata) equivalent of the above-describedwriting current Ia (the gradation sequence current Idata). Thereby, thelight emission drive current Iem corresponding to a predetermined lightemission state (the luminance gradation sequence) is supplied on thebasis of the voltage component Va written (held) in the writingoperation time period Twr, and the organic EL element OEL maycontinuously emit light at a desired luminance gradation sequence inaccordance with the display data (the gradation sequence current Idata).

In this way, according to the light emission drive circuit and its drivecontrol method of the present embodiment, the drive control method in acurrent designation system to perform the light emission at apredetermine luminance gradation sequence is applied in such a mannerthat the gradation sequence current Idata (the writing current Ia)designating the current value in accordance with the light emissionstate (the luminance gradation sequence) of the organic EL element OELis compulsorily supplied between the drain and the source of the drivetransistor Tr 13 in the writing operation time period and the lightemission drive current Iem to flow through the organic EL element OEL iscontrolled based on the voltage component between the gate and thesource of the drive transistor Tr 13 held in accordance with its currentvalue. Further, both of the function to convert the current level of thegradation sequence current Idata in accordance with the desired displaydata (the luminance gradation sequence) into the voltage level (thecurrent and voltage conversion function) and the function to supply thelight emission drive current Iem having a predetermined current value tothe organic EL element OEL are realized by the single transistor for thelight emission driving (the drive transistor Tr 13 ). Therefore, it ispossible to realize a desired light emission property stably for a longtime without the affection such as variation of the operational propertyand the temporal change of each transistor composing the light emissiondrive circuit DC.

In addition, according to the light emission drive circuit and its drivecontrol method of the present embodiment, the precharge operation isperformed prior to the writing operation of the display data into thedisplay pixel EM and the light emission operation of the organic ELelement OEL. Thereby, not the minute current like the gradation sequencecurrent Idata but the electric charges equivalent to the drivetransistor precharge voltage Vpre13 exceeding the threshold voltageVth13 of the transistor is compulsorily accumulated once in thecapacitor Cs connected between the gate and the source of the transistorfor the light emission driving (the drive transistor Tr 13 ) provided inthe light emission drive circuit DC at the precharge voltage Vpre. Then,the drive transistor Tr 13 turns off the selection transistor Tr 12 sothat the drive transistor Tr 13 decreases into each of the thresholdVth13 by performing the threshold correction operation. Consequently,after the threshold correction operation is terminated, it is possibleto accumulate the electric charges equivalent to the threshold Vth13 ofthe drive transistor Tr 13 of the light emission drive circuit DC in thecapacitor Cs of each light emission drive circuit DC and hold it.

In this way, even if variation is generated in the threshold Vth13 ofeach drive transistor Tr 13, the electric charges in accordance with thethreshold Vth13 of each drive transistor Tr 13 is appropriately chargedin the threshold correction operation. Then, in the writing operation ofthe display data, it is not necessary to charge the capacitor Cs by thegradation sequence current Idata on the basis of the display data so asto be equivalent to the threshold voltage Vth13 and it is only necessaryto add and accumulate (charge) the voltage component Vdata in accordancewith this display data (the gradation sequence current Idata).Therefore, the electric charges based on the display data can be quicklyaccumulated (charged) in the capacitor Cs and lack of the writing can beprevented. Accordingly, it is possible to make the organic EL elementOEL to perform the light emission operation at the appropriate luminancegradation sequence in accordance with the display data.

Specifically, in the light emission drive circuit applying the currentdesignation system as shown in the present embodiment, the current valueof the gradation sequence current Idata (the writing current Ia) to besupplied to the light emission drive circuit DC upon the writingoperation (in the present embodiment, draws the current in the lightemission drive circuit DC) is approximately equal to the light emissiondrive current Iem flowing through the organic EL element OEL.

Therefore, when performing the display operation at the low luminancegradation sequence (when making the organic EL element OEL to performthe light emission operation at the low luminance gradation sequence),the current value of the gradation sequence current Idata to be suppliedto the signal drive circuit SDR is made very small.

On the other hand, time allowed for the writing operation into thedisplay pixel (the light emission drive circuit) has been generallydefined in advance on the basis of the specification (the frame time andthe number of scan lines) of the display panel (to be described indetail later with reference to the application example to the displayunit).

Therefore, in the case of supplying the gradation sequence current Idatain accordance with the display data in the writing operation time periodwithout performing the precharge operation and the threshold correctionoperation according to the present embodiment and forming apredetermined potential between the gate and the source (equivalent tothe opposite ends of the capacitor Cs) of the transistor for the lightemission driving (equivalent to the drive transistor Tr 13 ), first, theelectric charges for the threshold voltage Vth13 of the transistor isnecessarily accumulated. For this reason, the sufficient electric chargecorresponding to the threshold voltage Vth13 and the other capacitance(for example, the parasitic capacitance of the data line DL and thethreshold voltage Vth12 of the selection transistor Tr 12) is notaccumulated between the gate and the source of this transistor at theminute gradation sequence current Idata in accordance with the lowluminance gradation sequence display, which leads to the face that thelight emission drive current Iem having the current value in accordancewith this gradation sequence current Idata cannot be supplied to thelight emission element (the organic EL element OEL).

Thereby, the current value of the light emission drive current Iem (theoutput gradation sequence) shared by the organic EL element OEL withrespect to the gradation sequence current Idata (the writing current Ia;the input gradation sequence) to be supplied to the light emission drivecircuit DC indicates nonlinearity in the low luminance gradationsequence range as shown by a circle in FIG. 8. This makes impossible toperform the light emission operation at the appropriate luminancegradation sequence in accordance with the display data.

On the contrary, according to the light emission drive circuit and itsdrive control method of the present invention, prior to the writingoperation of the display data, the light emission drive circuit isdriven controlled to perform the precharge operation and the thresholdcorrection operation for accumulating the electric charges equivalent tothe threshold voltage between the gate and the source (the opposite endsof the capacitor Cs) of the drive transistor (transistor for the lightemission driving) Tr 13. Therefore, for example, as shown in FIGS. 9Aand 9B, the output gradation sequence (the light emission drive currentIem; the light emission luminance) with respect to the input gradationsequence (the gradation sequence current Idata; the writing current Ia)shows a good linearity even in the low luminance gradation sequencerage, so that the light emission operation can be carried out at theappropriate luminance gradation sequence in accordance with the displaydata.

Particularly, according to the light emission drive circuit and itsdrive control method of the embodiment, as shown in FIGS. 9A and 9B, ithas been confirmed that the output gradation sequence with respect tothe input gradation sequence shows a sublinearity even if the thresholdvoltage Vth13 of the drive transistor Tr 13 is changed (shifted) due tothe temporal change and the light emission history or the like. FIG. 8is a graph showing a changing trend of a light emission drive currentagainst a gradation sequence current in a contrast example with a drivecontrol method of the light emission drive circuit according to theembodiment, and FIGS. 9A and 9B are graphs showing a changing trend ofan output gradation sequence against an input gradation sequence in thedrive control method of the light emission drive circuit according tothe embodiment. In FIGS. 9A and 9B, a horizontal axis represents agradation sequence value on the basis of the gradation sequence currentIdata, a vertical axis represents a gradation sequence value on thebasis of the light emission drive current Iem generated from thegradation sequence current Idata, and a broken line represents an idealvalue. In this case, FIG. 9A is a graph showing a changing trend of anoutput gradation sequence value against an input gradation sequencevalue under the initial state that no change is generated in thethreshold voltage of the drive transistor Tr 13. FIG. 9B is a graphshowing a changing trend of an output gradation sequence value againstan input gradation sequence value under the state that the thresholdvoltage of the drive transistor Tr 13 is shifted by 4V due to thetemporal change. In this way, the low gradation sequence is notcollapsed not like FIG. 8 and it is possible to acquire the linear lightemission drive current Iem with respect to the gradation sequencecurrent Idata.

(Drive control method of light emission drive circuit

(Gradation sequence display: (2)) Next, a second example (the gradationsequence display operation) of a drive control method in a lightemission circuit having the structures will be described below.

FIG. 10 is a timing chart showing the current value of the data line DL;a potential of the selection signal Ssel; a potential of the hold signalShld; a potential of the supplying voltage Vsc; the potential differencein the opposite ends of the capacitor Cs; and the current value of thelight emission drive current Iem in the second example of the drivecontrol operation of the light emission drive circuit according to theembodiment. FIGS. 11A and 11B are conceptual drawings showing theoperation example (precharge operation/voltage correction operation) ofthe light emission drive circuit according to the embodiment. FIGS. 12Aand 12B are conceptual drawings showing the operation example (writingoperation/light emission operation) of the light emission drive circuitaccording to the embodiment. Here, referring to the drive controlcircuit (FIG. 1) shown in the embodiment, the explanation of the controloperation equivalent of the drive control method shown in the firstexample (FIGS. 2, 3A, 3B, and 4) will be herein simplified.

According to the drive control method shown in the first example, thedrive control method provided with the threshold correction operationtime period Tth to correct the charging voltage of the capacitor Cs sothat the charging voltage decreases from the drive transistor prechargevoltage Vpre13 into the threshold value voltage Vth13 of the drivetransistor Tr 13 after the precharge operation time period Tpre forcharging the drive transistor precharge voltage Vpre13 in the capacitorCs connected between the gate and the source of the drive transistor Tr13 as the transistor for the. light emission driving is indicated.However, the present invention is not limited to this method.

According to the drive control method shown in the first example, therehas been explained the case of applying the method of accumulating theelectric charges amount equivalent to the threshold voltage Vth13between the gate and the source (the capacitor Cs) of the transistor forthe light emission driving (the drive transistor Tr 13 ) prior to thewriting operation; and adding the all of the electric charges by thegradation sequence Idata to be supplied upon the writing operation tothe electric charges amount equivalent to the threshold voltage Vth13and accumulating them as the electric charges serving to generate thelight emission drive current Iem. In this case, the voltage exceedingthe threshold voltage Vth13 is applied between the gate and the sourceof the drive transistor Tr 13 and the electric charges is accumulatedtherein in the precharge operation time period Tpre. Then, the electriccharges is discharged till the voltage decreases into the thresholdvoltage Vth13 in the threshold correction operation time period Tth.Therefore, if the difference voltage between the voltage applied betweenthe gate and the source of the drive transistor Tr 13 and the thresholdvoltage Vth13 is large, the threshold correction operation time periodTth becomes long.

According to the present embodiment, based on such a technical idea, thedrive control method is carried out, as shown in FIG. 10, by setting thelight emission drive circuit so as to include a precharge operation timeperiod Tpre of accumulating the electric charges based on the drivetransistor precharge voltage Vpre13 in the capacitor Cs of the lightemission drive circuit DC within one processing cycle time period Tcyc;a voltage correction operation time period Tvt of partially dischargingthe electric charges accumulated in the capacitor Cs and remaining theelectric charges equivalent to the voltage (the minimum luminancevoltage Vlsb) to generate the light emission drive current Iem whenmaking the organic EL element OEL to perform the light emission at theminimum luminance gradation sequence (the gradation sequence, of whichluminance except for the no-light emission is the minimum) in thecapacitor Cs between the gate and the source of the drive transistor Tr13 and holding the electric charges; a writing operation time period Twrof writing the electric charges on the basis of the gradation sequencesignal (the gradation sequence current Idata) in accordance with thedisplay data in the capacitor Cs; and a light emission operation timeperiod Tem of making the organic EL element to perform the lightemission operation at a predetermined luminance gradation sequence onthe basis of the electric charges accumulated in the capacitor Cs(Tcyc≧Tpre+Tth+Tvt+Twr+Tem).

Here, the one processing cycle time period Tcyc is a time periodrequired in order for a row of a display pixel EM to display the imagefor one row in the image of one frame in the case of displaying theimage of one frame by arranging a plurality of display pixels EM in amatrix in row and column directions. The precharge operation timeperiods Tpre and the voltage correction operation time periods Tvt maybe acquired at the same time in plural rows and the light emissionoperation time periods Tem may be acquired at the same time in pluralrows while deviating the writing operation time period Twr to write thedata for each row.

In other words, a drive control method is applied to set the electriccharges accumulated between the gate and the source (the capacitor Cs)of the transistor for the light emission driving (the drive transistorTr 13 ) after the precharge operation time periods Tpre that the switchmeans SM of the signal drive circuit SDR outputs the precharge voltageVpre to the data line DL and before moving to the writing operation timeperiod Twr that the switching means SM of the signal drive circuit SDRflows the gradation sequence current Idata to the data line DL not atthe value equivalent to the threshold voltage Vh13 but at the valueequivalent to the voltage (the minimum luminance voltage Vlsb) forgenerating the light emission drive current when performing the lightemission operation at the minimum luminance gradation sequence.

Specifically, as shown in FIG. 10, the voltage correction operation timeperiod Tvt to be carried out after the precharge operation time periodis set so as to stop the voltage correction operation and move to thefollowing writing operation time period Twr when attaining to thegate-to-source voltage Vgs (=the minimum luminance voltage Vlsb; thefirst potential difference) capable of flowing the light emission drivecurrent Iem (=Ilsb; 4.68E−08A) upon performing the light emissionoperation at the minimum luminance gradation sequence (approximately,100 to 200 μsec) in the changing trend of the gate-to-source voltage Vgs(the opposite ends' voltage of the capacitor Cs) of the drive transistorTr 13 shown in FIG. 6 and the changing trend of the drain-to-sourcevoltage Ids (the light emission drive current Iem) of the drivetransistor Tr 13 shown in FIG. 7.

According to such a drive control method of the light emission drivecircuit, in the voltage correction operation time period Tvt after theprecharge operation time period Tpre, it is only necessary to decreasethe drive transistor precharge voltage Vpre13 charged in the capacitorCs once into the minimum luminance voltage Vlsb in accordance with thelight emission drive current Iem (=Ilsb) required to make the organic ELelement OEL to perform the light emission operation (the displayoperation) at the minimum luminance gradation sequence, which is thevoltage higher than the threshold voltage Vth13 of the drive transistorTr 13 (namely, the voltage having the large absolute value). For thisreason, the potential difference between the drive transistor prechargevoltage Vpre13 and the minimum luminance voltage Vlsb is smaller thanthe potential difference between the potential difference between thedrive transistor precharge voltage Vpre13 and the threshold voltageVth13. This leads to the fact that the voltage correction operation timeperiod Tvt is shorter than the threshold correction operation timeperiod Tth. For example, if the drive transistor Tr 13 in the changingtrend of the gate-to-source voltage Vgs (the opposite ends' voltage Vcof the capacitor Cs) shown in FIGS. 6 and 7 is employed, it is possibleto largely reduce time required for the correction operation of thecharging voltage (about 100 to 200 μsec) as compared to time till thevoltage decreases into the threshold voltage Vth13 (approximately, 3 to4 μsec).

In addition, in the voltage correction operation time period Tvt, notonly the electric charges is accumulated in the capacitor Cs but alsothe electric charges is accumulated so that the gradation sequencecurrent Idata flows in the other capacitance of the current route fromthe supplying voltage line VL to the data line DL other than thecapacitor Cs. Therefore, even when the minute gradation sequence currentIdata is accumulated on the basis of the display data in the followingwriting operation time period Twr, it is possible to add the electriccharges serving to generate the light emission drive current Iem withoutdelay by means of the current Idata to the electric charges equivalentto the minimum luminance voltage Vlsb accumulated in the capacitor Csand to quickly and sufficiently accumulate (write) the voltage componentVdata appropriately corresponding to the display data.

Accordingly, in the one processing cycle time period Tcyc according tothe drive control operation (the light emission operation of the lightemission element) of the light emission drive circuit, it is possible toreduce time required for the correction operation of the chargingvoltage Vc of the capacitor Cs (the gate-to-source voltage Vgs) carriedout prior to the writing operation time period Twr and the lightemission operation time period Tem. This enables to set the lightemission operation time period Tem of the light emission elementrelatively long, to improve the light emission luminance, as same as thecase shown in FIG. 9, to prevent the reduction of the light emissionluminance in the low luminance gradation sequence range, and to maintaina linearity. (Drive control method of light emission drive circuit(no-light emission display)) Subsequently, a third example (the no-lightemission display operation) of the drive control method in the lightemission drive circuit having the structures will be described below.

FIG. 13 is a timing chart showing the current value of the data line DL;the potential of the selection signal Ssel; the potential of the holdsignal Shld; the potential of the supplying voltage Vsc; the potentialdifference at the opposite ends of the capacitor Cs; and the currentvalue of the light emission drive current Iem flowing through theorganic EL element OEL according to a third example of the drive controloperation of the light emission drive circuit according to theembodiment. In the meantime, in the data line DL, the direction of thewriting current Ia flowing till the precharge current Ipre and theopposite ends' potential Vc of the capacitor Cs becomes 0V due to theno-light emission display voltage Vzero (to be described later) areinversed with each other. FIGS. 14A and 14B are conceptual drawingsshowing the operation example (writing operation/light emissionoperation) of the light emission drive circuit according to theembodiment. Here, the explanations of the control operations equivalentof the drive control methods shown in the first and second examples(FIGS. 2, 3A, 3B, 10, and 11) will be herein simplified.

In any case of the first and second examples, the supplying voltage Vscmay be displaced from the low potential selection voltage value Vs intothe high potential light emission voltage value Ve upon moving from thewriting operation time period Twr to the light emission operation timeperiod Tem. Therefore, the electric charges such as a parasiticcapacitance of the holding transistor Tr 11 is displaced and the gatepotential of the drive transistor Tr 13 is increased.

According to the first and second examples, even if the charging voltageVc written in the capacitor Cs is located in the vicinity of thethreshold voltage Vth13 in the voltage correction operation time periodTvt of the prior one processing cycle time period Tcyc, the lightemission drive current Iem flows by such a slight gate potentialdisplacement, and the no-light emission operation may be unstable. Forthis reason, it is preferable that this charging voltage Vc iscompletely discharged, and the gate-to-source voltage Vgs of the drivetransistor Tr 13 is set at 0V (the contact N11 and the contact N12 hasthe same potential). In the case where such writing operation is carriedout by using the gradation sequence current Idata of the minute currentvalue, it takes relatively long time till the writing current Ia becomeszero and the electric charges of the capacitor Cs is discharged.Particularly, the more the charging voltage Vc written in the capacitorCs is near the maximum luminance gradation sequence voltage Vmsb in thevoltage correction operation time periods Tvt of the prior oneprocessing cycle time period Tcyc, the more the electric charges amountheld in the capacitor Cs is, so that it takes more long time.

According to the drive control method shown in the above-describe firstexample, the method to accumulate the electric charges equivalent of thethreshold voltage Vth13 in the capacitor Cs connected between the gateand the source of the drive transistor Tr 13 as the transistor for thelight emission driving prior to the writing operation. Accordingly, asshown in FIG. 6, relatively long time about 3 msec is necessary till thegate-to-source voltage Vgs (the opposite ends' potential Vc of thecapacitor Cs) decreases into the threshold voltage Vth13. In addition,in order to realize the no-light emission display operation to hold theorganic EL element in the no-light emission state in the light emissionoperation time period Tem, it is necessary to set the voltage (theopposite ends' potential Vc) charged in the capacitor Cs by thegradation sequence current Idata to be supplied in the writing operationtime period Twr after threshold correction time period Tth is terminated(namely, after laps of 3 msec) at the value less than the thresholdvoltage Vth13.

In the same way, according to the drive control method shown in thesecond example, the method to accumulate the electric charges equivalentof the minimum luminance voltage Vlsb in the capacitor Cs connectedbetween the gate and the source of the drive transistor Tr 13 prior tothe writing operation is employed. Accordingly, as shown in FIG. 6, theoperation to correct the charging voltage Vc of the capacitor Cs can beapproximately reduced to about 100 to 200 μsec. However, in order torealize the no-light emission display operation, it is necessary to setthe voltage (the opposite ends' potential Vc) charged in the capacitorCs at the value less than the threshold voltage Vth13 by the gradationsequence current Idata supplied in the writing operation time periodTwr.

Thus, according to the present embodiment, as shown in FIG. 13, thedrive control method is carried out by setting the light emission drivecircuit so as to include the precharge operation time period Tpre toaccumulate the electric charges based on the precharge voltage Vpre inthe capacitor Cs of the light emission drive circuit DC within the oneprocessing cycle time period Tcyc; the voltage correction operation timeperiod Tvt to remain the electric charges equivalent of the minimumluminance voltage Vlsb or the electric charges equivalent of thethreshold value voltage Vth13 and to hold it while partially dischargingthe electric charges accumulated in the capacitor Cs; the writingoperation time period Twr to apply the gradation sequence signal (theno-light emission display voltage Vzero) in accordance with the no-lightemission display data and to discharge most of the electric charges heldin the capacitor Cs; and the light emission operation time period Tem toprevent the organic EL element OEL from performing the light emissionoperation (to make the organic EL element OEL to perform the no-lightemission operation) (Tcyc >Tpre +Tvt +Twr +Tem).

In other words, as same as the embodiment shown in the first example orthe second example, the drive control method is employed to set theelectric charges accumulated between the gate and the source (thecapacitor Cs) of the transistor for the light emission driving (thedrive transistor Tr 13 ) at the value equivalent of the thresholdvoltage Vth13 at once or the value equivalent of the voltage (theminimum luminance voltage Vlsb) for generating the light emission drivecurrent upon performing the light emission operation at the minimumluminance gradation sequence (LSB) in the precharge operation and thevoltage correction operation prior to the writing operation time periodTwr and set the gate-to-source voltage Vgs (the opposite ends' potentialVc of the capacitor Cs) at 0V by directly applying the no-light emissiondisplay voltage Vzero equivalent to the selection voltage value Vs asthe supplying voltage Vsc from the signal drive circuit SDR to the lightemission drive circuit DC (the contact point N12 ) via the data line DLas shown in FIG. 14A in the following writing operation.

Thereby, the almost all of the electric charges accumulated in thecapacitor Cs are discharged and the gate-to-source voltage Vgs of thedrive transistor Tr 13 is set at the sufficiently lower voltage value(about 0V) than the threshold voltage Vth13. Consequently, even if thesupplying voltage Vsc is displaced from the low potential selectionvoltage value Vs to the high potential light emission voltage value Veand the gate potential of the drive transistor Tr 13 is slightlyincreased upon moving from the writing operation time period Twr intothe light emission operation time period Tem, the gate-to-source voltageof the drive transistor Tr 13 is sufficiently lower than the thresholdvoltage Vth13. Therefore, as shown in FIG. 14B, the drive transistor Tr13 is not turned on (held in the off state) and the light emission drivecurrent Iem is not supplied to the organic EL element OEL, so that thelight emission operation is not carried out (becomes the no-lightemission state).

Here, timing for applying the no-light emission display voltage Vzerofrom the signal drive circuit SDR to the light emission drive circuit DCis set at the time when the gate-to-source voltage Vgs attains to thethreshold voltage Vth13 or the minimum luminance voltage Vlsb in thewriting operation time period Twr as same as the embodiment shown in thefirst example or the second example. Therefore, the timing is set insuch a manner that, in the voltage correction operation time period Tvtafter the precharge operation, for example, when about 100 to 200 μsecelaps after staring the correction operation in the graph shown in FIG.6, terminating the voltage correction operation time period Tvt andmoving to the writing operation time period Twr, the no-light emissiondisplay voltage Vzero is applied.

Thereby, it is possible to largely reduce time that is necessary for theprecharge operation and the voltage correction operation carried outprior to the writing operation. Further, as compared to the case thatthe gradation sequence current in accordance with the no-light emissiondisplay data is supplied via the data line DL upon the no-light emissiondisplay operation (the no-light emission operation) and the almost allof the electric charges accumulated in the capacitor Cs that isconnected between the gate and the source of the drive transistor Tr 13is discharged, it is possible to well realize the no-light emissiondisplay operation while largely reducing time necessary for the writingoperation of the no-light emission display data. Accordingly, inaddition to the normal gradation sequence display operation in theembodiment shown in the first example or the second example, theno-light emission display operation in the embodiment shown in the thirdexample is controlled to be switched in accordance with the display dataand this makes it possible to realize the light emission operation ofthe desired number of the gradation sequences (for example, 256gradation sequences) with a relatively high luminance and withsharpness.

Specifically, according to the first example, the switch means SM of thesignal drive circuit SDR shown in FIG. 1 may output the prechargevoltage Vpre to the data line DL in the precharge operation time periodTpre. Then, in the writing operation time period Twr after the thresholdcorrection operation time period Tth, the switching means SM may outputthe no-light emission display voltage Vzero to the data line when thedisplay data is the no-light emission display and may perform switchingso that the gradation sequence current Idata flows through the data lineDL when the display data is the light emission display.

In the same way, according to the second example, the switch means SM ofthe signal drive circuit SDR shown in FIG. 1 may output the prechargevoltage Vpre to the data line DL in the precharge operation time periodTpre. Then, in the writing operation time period Twr after the voltagecorrection operation time period Tvt, the switch means SM may output theno-light emission display voltage Vzero to the data line DL when thedisplay data is the no-light emission display, and it may performswitching so that the gradation sequence current Idata flows through thedata line DL when the display data is the light emission display.

In addition, the embodiment (the drive control method) shown in the eachexample is described with reference to the circuit structure providedwith three transistors Tr 11 to Tr 13 as the light emission drivecircuit DC, as shown in FIG. 1. However, it is obvious that the presentinvention is not limited to this and the other circuit structure isavailable if it is a light emission drive circuit in accordance with acurrent designation system and it can effect a current and voltageconversion function to convert a gradation sequence current supplied inaccordance with the display data into a voltage component by using asingle thin film transistor and accumulate the voltage component in acapacitor connected between a gate and a source or a parasiticcapacitance and a light emission drive function to control a lightemission drive current to be supplied to a light emission element (anorganic EL element) on the basis of the accumulated voltage component.(Display unit) Next, a display unit provided with a display panel havinga plurality of display pixels having the light emission drive circuitsarranged in a matrix and its display drive method and its display drivemethod will be described with reference to the drawings below.

FIG. 15 is a schematic block diagram showing an example of the entirestructure of a display unit according to the embodiment. FIG. 16 is aschematic block diagram showing a display panel to be applied to thedisplay unit according to the embodiment and an example of itsperipheral circuit (a selection driver, a holding driver, and asupplying voltage driver). Here, the display unit provided with afunction to selectively perform the gradation sequence display operationshown in the above described first or second example and the no-lightemission display operation shown in the third example will be described.In addition, the structure equivalent of the display pixel (the lightemission drive circuit; refer to FIG. 1) is given the same or the equalreference numeral or mark to simplify its explanation.

As shown in FIGS. 15 and 16, a display unit 100 according to the presentembodiment is configured so as to include a display panel 110 arrangedin a matrix composed of n rows x m columns (n, m is an arbitrarypositive integer) of plural display images provided with the lightemission drive circuit DC having the same circuit structure as theembodiment and the organic EL element (the light emission element) OELlocated in the vicinity of each intersection point between the pluralselection lines SL arranged in approximately a row direction and theplural data lines DL arranged in a column direction; a selection driver120 that is connected to the selection line SL of this display panel 110for sequentially applying a selection signal (a writing controlterminal) Ssel for each selection line SL at predetermined timing; aholding driver 130 that is connected to a hold line HL arranged in therow direction in parallel with each of the selection lines SL forsequentially applying the hold signal (the voltage control signal) Vhidat predetermined timing; a data or signal driver 140 that is connectedto the data line DL of the display panel 110 for supplying the prechargevoltage Vpre to the display pixel EM via each data line DL in theprecharge operation Tpre and supplying the gradation sequence signal(the gradation sequence current Idata or the no-light emission displayvoltage Vzero) in accordance with the display data to the display pixelEM via each data line DL in the writing operation time period Twr; asupplying voltage driver 150 that is connected to the supplying voltageline VL connected to the all display pixels EM arranged in the displaypanel 110 in common for applying a predetermined supplying voltage Vscto the supplying voltage line VL; a system controller 160 for generatinga selection control signal to control the operation states of at leastthe selection driver 120 and the holding driver 130, the data driver140, and the supplying voltage driver 150 on the basis of the timingsignal to be supplied from a display signal generation circuit 170 to bedescribed later; the hold control signal, the data control signal, and apower source control signal and outputting them; and the display signalgeneration circuit 107, which generates the display data (the luminancegradation sequence data), for example, on the basis of the image signalto be supplied from the outside of the display unit 100 and supplies itto the data driver 140, extracts or generates a timing signal (thesystem clock or the like) for displaying predetermine image informationon the display panel 110 on the basis of the display data and suppliesit to the system controller 160.

The each configuration will be specifically described below. (Displaypanel) As same as the embodiment (refer to FIG. 1), the display pixel EMarranged in the display panel 110 shown in FIG. 16 is configured so asto have a selection signal Ssel to be applied from the selection driver120 via the selection line SL and a hold signal Shld to be applied fromthe holding driver 130 via the hold line HL; a gradation sequence signalto be supplied from the signal driver 140 via the data line DL (thegradation sequence current Idata or the no-light emission displayvoltage Vzero); the light emission drive circuit DC that carries out theprecharge operation and the threshold correction operation (or thevoltage correction operation) described in the each drive controlmethod, the writing operation, and the light emission operation on thebasis of the supplying voltage Vsc to be applied from the supplyingvoltage driver 150 via the supplying voltage line VL; and the organic ELelement (light emission element) OEL performing the light emissionoperation at a predetermined luminance gradation sequence in accordancewith the current value of the light emission drive current Iem to besupplied from this light emission drive circuit DC. In the meantime,according to the present embodiment, the case that the organic ELelement OEL is applied as the light emission element will be described,as same as the embodiment (refer to FIG. 1). However, the other lightemission element is available if it is a current control type of a lightemission element to perform the light emission operation at apredetermined luminance gradation sequence in accordance with thecurrent value of the light emission drive current. (Selection driver)The selection driver 120 sets the display pixel EM for each row at theselection state by applying the on-level selection signal Ssel to eachselection line SL on the basis of the selection control signal to besupplied from the system controller 160. According to the display unitof the embodiment (to be described in detail later with reference to thedrive control method (refer to FIG. 20)), in the precharge operationtime period, applying the selection signal Ssel to at least plural rowsof selection lines SL, preferably, to the all rows of selection lines SLsimultaneously, plural rows of the display panel 110, preferably, theall display pixels EM are set at the selection state at the same time.On the other hand, in the panel writing operation time period, theselection signal Ssel is sequentially applied to each row of theselection line SL, whereby the display pixel EM for each row issequentially controlled so as to be set at the selection state.

For example, as shown in FIG. 16, the selection driver 120 is configuredso as to have a shift resistor 121 for sequentially outputting a shiftsignal in accordance with each row of the selection line SL on the basisof a selection clock signal SCK to be supplied from the systemcontroller 160 to be described later and a selection start signal SST asa selection control signal; and an output circuit section 122 thatconverts a shift signal outputted from this shift resistor 121 into apredetermined signal level (the on-level) and outputs this shift signalto each selection line SL as the selection signal Ssel on the basis ofan output control signal SOE supplied from a system controller 160 as aselection control signal.

Here, in the selection driver 120 according to the present embodiment,particularly, the output circuit section 122 is configured so as to havea function (mode) to sequentially output a shift signal sequentiallyoutputted from the shift resister 121 to each row of the selection lineSL as the on-level selection signal Ssel; and a function (mode) forsimultaneously outputting the on-level selection signal Ssel to at leastplural rows of the selection lines SL, preferably, the all selectionlines SL regardless of the shift signal from the shift resistor 121, andon the basis of the output control signal SOE, these functions areconfigured allowed to be switched.

In other words, as described in later, in the operation for supplyingthe gradation sequence signal to each row of display pixel EM arrangedon the display panel 110 and sequentially writing the display datatherein (the panel writing operation), the output circuit section 122 isset at the mode to sequentially output the selection signal Ssel to eachselection line SL. In the operation for accumulating (charging) theelectric charges in accordance with a predetermined precharge voltageVpre in at least plural rows of the selection lines SL arranged on thedisplay panel 110, preferably, in the all display pixels EM prior to thepanel writing operation, the output circuit section 122 is set at themode to simultaneously output the selection signal Ssel to at leastplural rows of the selection lines SL, preferably, the all selectionlines SL.

(Holding driver)

The holding driver 130 may hold the applying state of a predeterminedvoltage to a gate terminal of a transistor for the light emissiondriving provided to the display pixel EM for each row (corresponding tothe light emission drive circuit Tr 13 shown with reference to theembodiment) by applying the on-level hold signal Shld to each hold lineHL on the basis of the hold control signal supplied from the systemcontroller 160.

According to the display unit of the embodiment (to be described indetail later with reference to the drive control method (refer to FIG.20)), in the precharge operation time period and the thresholdcorrection operation time period (or the voltage correction timeperiod), the hold signal Shld is applied to at least plural rows of holdlines HL, preferably, to the all rows of hold lines HL simultaneously.Then, plural rows of the display panel 110, preferably, the all displaypixels EM are set at the selection state at the same time. On the otherhand, in the panel writing operation time period, the hold signal Shldis sequentially applied to each row of the hold line HL, whereby thedisplay pixel EM for each row is sequentially controlled so as to holdthe gate voltage of the transistor for the light emission drivingprovided to the display pixel EM for each row.

For example, as shown in FIG. 16, as same as the selection drier 120,the hold driver 130 is configured so as to have a shift resistor 131 forsequentially outputting a shift signal corresponding to the hold line HLof each row on the basis of a hold clock signal HCK and a hold startsignal HST to be supplied from the system controller 160 as a holdcontrol signal and an output circuit section 132 for converting thisshift signal into a predetermined signal level (on level) and outputtingthe shift signal to each hold line HL as the hold signal Shld on thebasis of an output control signal HOL to be supplied as the hold controlsignal.

Here, in the hold driver 130 according to the present embodiment,particularly, the output circuit section 122 is configured so as to havea function (mode) to sequentially output a shift signal sequentiallyoutputted from the shift resister 121 to each row of the hold line HL asthe on-level hold signal Shld; and a function (mode) for simultaneouslyoutputting the on-level hold signal Shld to at least plural rows of thehold lines HL, preferably, the all hold lines HL regardless of the shiftsignal from the shift resistor 121, and on the basis of the outputcontrol signal HOE, these functions are configured allowed to beswitched.

In other words, as described later, in the operation for supplying thegradation sequence signal to each row of display pixel EM arranged onthe display panel 110 and sequentially writing the display data therein(the panel writing operation), the output circuit section 122 is set atthe mode to sequentially output the hold signal Shld to each hold lineHL. In the operation for accumulating (charging) the electric charges inaccordance with a predetermined precharge voltage Vpre in at leastplural rows of the display pixels EM arranged on the display panel 110,preferably, in the all display pixels EM prior to the panel writingoperation and the.operation for partially discharging the accumulatedelectric charges, remaining the electric charges corresponding to thethreshold voltage Vth13 (or the minimum luminance voltage Vlsb), andholding it, the output circuit section 122 is set at the mode to outputthe hold signal Shld to at least plural rows of the hold signals HL,preferably, the all hold signals HL. (Data driver) FIG. 17 is aschematic block diagram showing an example of a data driver that can beapplied to the display unit according to the embodiment. FIG. 18 is aschematic block diagram showing an example of a gradation sequencesignal generating section that can be applied to the data driveraccording to the embodiment. FIG. 19 is a schematic block diagramshowing the structures of substantial parts of a gradation sequencesignal generating section that can be applied to the data driveraccording to the embodiment. In the meantime, with respect to the innerstructure of the data driver shown in FIGS. 17 to 19, the applicableexample is only shown and the present embodiment is not limited to this.

As outlined in FIG. 17, a data driver 140 is configured so as to have agradation sequence signal generating section 141 that sequentiallyfetches the display data (the luminance gradation sequence data)composed of a digital signal supplied from the display signal generationcircuit 170 to be described later for each row at a predetermined timingon the basis of a data control signal to be supplied from the systemcontroller 160 and holding it, generates the gradation sequence currentIdata having the current value corresponding to a gradation sequencevalue when the gradation sequence of the display data is a value otherthan 0 bit (namely, the no-light emission display), on the other hand,generates a specific voltage (the no-light emission display voltage)Vzero for performing the no-light emission display operation when thegradation sequence value is a value of 0 bit (the no-light emissiondisplay), and simultaneously supplies this specific voltage Vzero to thedisplay pixel EM of each row set at the selection state in the panelwriting operation time period via each data line DL; and a prechargevoltage supplying section 142 that controls the on and off operations ofa transistor switch SWpr of which one end is connected to each data lineDL on the basis of a data control signal (a precharge signal PCG) to besupplied from the system controller 160, and simultaneously supplies apredetermined precharge voltage Vpre to at least plural rows of thedisplay pixels EM arranged on the display panel 110, preferably, to theall display pixels EM via the each data line DL.

Here, for example, as shown in FIG. 18, the gradation sequence signalgenerating section 141 is configured so as to have a shift resistor 41for sequentially outputting a shift signal on the basis of the datacontrol signal (a shift clock signal CLK and a sampling start signalSTR) supplied from the system controller 160; a data resistor circuit 42for sequentially fetching the display data DO to Dm for one row to besupplied from the display signal generation circuit 170 on the basis ofinput timing of this shift signal; a data latch circuit 43 that holdsthe display data DO to Dm for one row fetched by the data resistorcircuit 42 on the basis of a data control signal (a data latch signalSTB); a no-light emission display voltage applying circuit 44 thatdetects the no-light emission display data (the gradation sequence valueof 0 bit) from the display data DO to Dm held by this data latch circuit43, applies a predetermined no-light emission display voltage Vzero tothe data line DL of a row corresponding to this display data, and passesthe display data DO to Dm other than the no- light emission display dataas they are and outputting it to a D/A converter 45 of the next stage; aD/A converter 45 that converts the display data DO to Dm (other than theno-light emission display data) inputted passing through the no-lightemission display voltage applying circuit 44 into a predetermined analogsignal voltage (the gradation sequence voltage Vpix) on the basis ofgradation sequence reference voltages VO to VP supplied from powersource supplying means (its illustration is herein omitted); and avoltage current converting and gradation sequence current supplyingcircuit 46 that generates the gradation sequence current Idatacorresponding to the displace data converted into the analog signalvoltage, and outputs it to the data line DL of a row corresponding tothis display data at timing based on a data control signal (an outputenable signal OE) to be supplied from the system controller 160.

Here, for example, as shown in FIG. 19, the no-light emission displayvoltage applying circuit 44 is configured so as to have a no-lightemission display data determining section 44a that detects the displaydata having the gradation sequence of 0 bit as the no-light emissiondisplay data among the display data DO to Dm composed of the digitaldata held in the data latch circuit 43 in accordance with each of thespecific rows; and a no-light emission display voltage generatingsection 44b that directly applies a predetermined no-light emissiondisplay voltage Vzero to the data line DL of the row that is determinedas the no-light emission display data without going through the D/Aconverter 45 of the next stage and the voltage current converting andgradation sequence current supplying circuit 46 of the next stage.

As indicated in the drive control method according to the third example,the no-light emission display voltage Vzero applied to the.data line DLby the no-light emission display voltage generating section 44b is setat an arbitrary voltage value necessary for making the gate-to-sourcevoltage Vgs into 0V (or brings it close to 0V) by discharging theelectric charges accumulated between the gate and the source of thetransistor for the light emission operation (the drive transistor Tr 13) of the light emission drive circuit DC configuring the display pixelEM due to the precharge operation and the threshold correction operation(or the voltage correction operation).

(Supplying voltage driver)

The supplying voltage driver 150 applies the supplying voltage Vsc ofthe high level light emission voltage value Ve to at least plural rowsof display elements EM, preferably, to the all display elements EM viathe supplying voltage line VL only in a period of time to make eachdisplay pixel EM (the organic EL element OEL) arranged in the displaypanel 110 on the basis of a power source control signal (a supplyingvoltage switch signal PWR) to be supplied from the system controller 160and the supplying voltage driver 150 applies the supplying voltage Vscof the low level selection voltage value Vs to at least plural rows ofdisplay pixels EM, preferably, to the all display pixels EM in the otherperiod of time.

The supplying voltage Vsc of the low level selection voltage value Vs isapplied from the supplying voltage driver 150 to at least plural rows ofdisplay pixels EM, preferably, to the all display pixels EM in theprecharge operation time period in which at least plural rows of displaypixels EM arranged in the display panel 110, preferably, the all displaypixels EM are simultaneously supplied to charge; in the thresholdcorrection operation time period (or the voltage correction operationtime period) in which the precharge voltage Vpre is partially dischargedand the threshold Vth13 (or the minimum luminance voltage Vlsb) is heldin at least plural rows of display pixels EM, preferably, to the alldisplay pixels EM; and the panel writing operation time period forsequentially setting the display pixel group EM of each row at theselection state and writing the gradation sequence signal (the gradationsequence current Idata or the no-light emission display voltage Vzero(specifically, described in detail later).

(System controller)

The system controller 160 may operate each driver at a predeterminedtiming by generating a selection control signal to control the operationstate of each of the selection driver 120 and the holding driver 130,the data driver 140, and the supplying voltage driver 150, a holdcontrol signal, a data control signal, and a power source control signaland outputting them to generate the selection signal Ssel and a holdsignal Shld having a predetermined voltage level, a gradation sequencesignal (the gradation sequence current Idata, the no-light emissiondisplay voltage Vzero), and a supplying voltage Vsc and output them; andmay continuously perform the drive control operation (the prechargeoperation, the threshold correction operation (or the voltage correctionoperation), the panel writing operation, and the light emissionoperation)) in each display pixel EM (the light emission drive circuitDC) to display predetermined image information based on an image signalon the display panel 110.

(Display signal generating circuit)

The display signal generation circuit 170 may extract a luminancegradation sequence signal component, for example, from the image signalto be supplied form the outside of the display unit 100 and may supplythis luminance gradation sequence signal component to the data resistorcircuit 42 of the data driver 140 as the display data (the luminancegradation sequence data) composed of the digital signal for each row ofthe display panel 110. Here, in the case where the image signal includesthe timing signal component to define the display timing of the imageinformation like a TV broadcast signal (a composite image signal), thedisplay signal generation circuit 170 may have a function to extract thetiming signal component and supply it to the system controller 160 otherthan a function to extract the luminance gradation sequence signalcomponent. In this case, the system controller 160 may generate eachcontrol signal to be individually supplied to the selection driver 120and the holding driver 130, the data driver 140, and the supplyingvoltage driver 150 on the basis of the timing signal supplied from thedisplay signal generation circuit 170. (Display drive method of displayunit) Next, a display drive method (the display operation of the imageinformation) in a display unit according to the present embodiment willbe described below.

FIG. 20 is a timing chart showing an example of the display drive methodof the display unit according to the embodiment. Here, the case to applythe drive control method shown in the second example and the thirdexample in the display pixel EM (the light emission drive circuit DC)shown in the embodiment (refer to FIG. 1) to the display unit of theembodiment will be described with reference to the display operation ofthe image information, and the description of the equivalent drivecontrol method is herein omitted.

The drive control operation of the display operation of the display unit100 according to the present embodiment, as shown in FIG. 20, is carriedout by setting the light emission drive circuit so as to include aprecharge operation time period TApr of accumulating the electriccharges corresponding to the precharge voltage Vpre in each displaypixel EM (the light emission drive circuit DC) by simultaneously settingat least plural rows of the display pixels EM displayed on the displaypanel 110, preferably, the all display pixels, EM at the selection stateand applying a predetermined precharge voltage Vpre from the prechargevoltage supplying section 142 provided in the data driver 140 via thedata line DL within one frame time period Tfr (equivalent to the oneprocessing cycle time period Tcyc); a voltage correction operation timeperiod TAvt of partially discharging the electric charges accumulated ineach display pixel EM and remaining the electric charges equivalent tothe voltage (the minimum luminance voltage) set in the transistor forthe light emission driving (equivalent to the voltage the drivetransistor Tr 13 ) when making the light emission element provided ineach display pixel EM (the organic EL element OEL) and holding theelectric charges; a writing operation time period TAwr of accumulatingthe electric charges corresponding to the gradation sequence signal ineach display pixel EM by setting the display pixels EM displayed on thedisplay panel 110 for each line at the selection state and applying thegradation sequence signal (the gradation sequence current Idata or theno-light emission display voltage Vzero) from the gradation sequencesignal generating section 141 provided in the data driver 140 via thedata line DL in accordance with the display data; and a light emissionoperation time period TAem of making the light emission elements (theorganic EL elements) to simultaneously perform the light emissionoperation at a luminance gradation sequence in accordance with thedisplay data on the basis of the electric charges accumulated in theeach display pixel EM (Tfr TApr +TAvt +TAwr +TAem). Here, the prechargeoperation time period TApr, the voltage correction operation time periodTAvt, the writing operation time period TAwr, and the light emissionoperation time period TAem are set so that they do not temporarilyoverlap with each other. (Precharge operation time period) First, in theprecharge operation time period TApr, as shown in FIG. 20, the on-levelselection signal Ssel is applied to at least plural rows of the displaypixels EM, preferably, the all selection lines SL from the selectiondriver 120, whereby at least plural rows of the selection line displayedon the display panel 110, preferably, the all display pixels EM aresimultaneously set at the selection state.

In addition, in synchronization with this timing, the low levelsupplying voltage Vsc (=Vs) is applied to at least plural rows of thedisplay pixels EM, preferably, the all display pixels EM from thesupplying voltage driver 150 via the common supplying voltage line VL,and the on-level hold signal Shld is applied to at least plural rows ofthe display pixels EM, preferably, the all hold lines HL from the holddriver 130. As a consequence, plural rows of the display pixels EM,preferably, the all display pixels EM are set at the hold state (indetail, the state that the voltage based on the low level supplyingvoltage Vsc is applied on a gate of the transistor for the lightemission driving (the drive transistor Tr 13 ) configuring the lightemission drive circuit DC shown in FIG. 1).

Then, a predetermined precharge voltage Vpre is applied to plural rowsof the data lines DL, preferably, the all data lines DL from theprecharge voltage supplying section 142 provided on the data driver 140in synchronization with this timing.

Consequently, the electric charges corresponding to the prechargevoltage Vpre is accumulated in the plural rows of the display pixels EM,preferably, the all display pixels EM (in detail, between the gate andthe source of the transistor for the light emission driving (the drivetransistor Tr 13 ) configuring the light emission drive circuit SC; theopposite ends of the capacitor Cs (refer to the opposite ends' potentialVc of each display pixel of FIG. 20). (Potential correction operationtime period) Next, in the voltage correction operation time period TAvt,as shown in FIG. 20, by holding the supplying voltage Vsc to be appliedfrom the supplying voltage driver 150 to each display pixel EM at a lowlevel (Vs) and applying the off-level selection signal Ssel to at leastplural rows of the selection liens SL, preferably, the all selectionlines SL from the selection driver 120 with the hold signal Shld to beapplied from the hold driver 130 to each display pixel EM held at the onlevel, at least plural rows of the display pixels EM, preferably, theall display pixels EM are simultaneously set at the no-selection state.

Thereby, as the drive control method shown in FIG. 2, the electriccharges accumulated in each display pixel EM (between the gate and thesource of the transistor for the light emission driving configuring thelight emission drive circuit DC; the opposite ends of the capacitor Cs)is partially discharged and the potential on the basis of the electriccharges accumulated (held) in the each display pixel EM (thegate-to-source voltage Vgs of the transistor for the light emissiondriving; the opposite ends' potential Vc of the capacitor Cs) is changedso as to decrease from the precharge voltage Vpre into the thresholdvoltage Vth13 of the transistor for the light emission driving (thedrive transistor Tr 13 ).

Here, in the voltage correction operation time period TAvt, when thepotential based on the electric charges accumulated (held) in eachdisplay pixel EM (the opposite ends' potential Vc of the capacitor Cs)is lowered to a voltage value (the minimum luminance voltage Vlsb) uponthe light emission operation of the light emission element (the organicEL element OEL) provided in each display pixel at the minimum luminancegradation sequence, this correction operation is terminated to move tothe following panel writing operation.

In other words, due to the series of precharge operation and voltagecorrection operation, the electric charges in accordance with theminimum luminance voltage Vlsb is accumulated in at least plural rows ofthe display pixels EM arranged on the display panel 110, preferably, theall display pixels EM (between the gate and the source of the transistorfor the light emission driving). (Panel writing operation time period)Subsequently, in the panel writing operation time period TAwr, as shownin FIG. 20, the on-level selection signal Ssel is sequentially appliedfrom the selection driver 120 to the selection line SL of each row sothat they do not temporarily overlap with each other, and the off-levelselection signal Ssel is applied to the selection line SL of theremaining row, whereby the display pixel EM of each row is sequentiallyset at the selection state.

In addition, the on-level hold signal Shld is sequentially applied tothe hold line HL of the row set at the selection state from the holddriver 130 in synchronization with this timing, and the off-level holdsignal Shld is applied to the hold line HL of the row that is notselected. Thereby, the display pixel EM of each row at the selectionstate is sequentially set at the hold state (the state that the voltageon the basis of the low-level supplying voltage Vsc (=Vs) is applied atthe gate of the transistor for the light emission driving (the drivetransistor Tr 13 )). In the meantime, in the panel writing operationtime period TAwr, following the precharge operation time period TApr andvoltage correction operation time period TAvt, the state that thelow-level supplying voltage Vsc (=Vs) is applied to at least plural rowsof the display pixels EM, preferably, the all display pixels EM from thesupplying voltage driver 150 is kept.

Then, the gradation sequence signal (the gradation sequence currentIdata or the no-light emission display voltage Vzero) on the basis ofthe display data (the digital data) supplied from the display signalgeneration circuit 170 is applied to at least plural rows of the datalines DL, preferably, the all data lines DL from the gradation sequencesignal generating section 141 provided in the data driver 140 insynchronization with this timing. Thereby, the voltage component basedon this gradation sequence signal is charged (written) in the displaypixel EM (between the gate and the source of the transistor for thelight emission driving; the opposite ends of the capacitor Cs) of therow set at the selection state.

Here, in the case where the display data to be supplied from the displaysignal generation circuit 170 to the data driver 140 is the luminancegradation sequence data other than the no-light emission display data(the gradation sequence value other than 0 bit) as same as the drivecontrol method shown in the second example and third example, thegradation sequence current Idata in accordance with this display data isgenerated by the data driver 140 to flow on the data line DL of thecorresponding row. On the other hand, when the display data to besupplied from the display signal generation circuit 170 is the no-lightemission display data (the gradation sequence value of 0 bit), apredetermined no-light emission display voltage Vzero is generated fromthe data driver 140 to be supplied to the data line DL of thecorresponding row. In FIG. 20, in order to explain the state that thosetwo kinds of gradation sequence signals are supplied, as an example, thecase is shown, in which the gradation sequence current Idata based onthe luminance gradation sequence data other than the no-light emissiondisplay data (the gradation sequence value other than 0 bit) is suppliedto the display pixels EM at jth column of first and nth rows, andfurther, the no-light emission display voltage Vzero based on theno-light emission display data (the gradation sequence value of 0 bit)is supplied to the display pixel EM at jth column of second row.Accordingly, in the display pixel EM to which the gradation sequencecurrent Idata is supplied as the gradation sequence signal, as shown inFIG. 20, the electric charges (the voltage component Vdata) based onthis gradation sequence signal is accumulated in addition to theelectric charges (the potential) in accordance with the minimumluminance voltage Vlsb held in each display pixel EX of thecorresponding row (between the gate and the source of the transistor forthe light emission driving). This results in that the voltage Va inaccordance with the display data is charged between the gate and thesource of the transistor for the light emission driving.

In addition, in the display pixel EM to which the gradation sequencecurrent Idata is supplied as the gradation sequence signal, as shown inFIG. 20, almost all of the electric charges in accordance with theminimum luminance voltage Vlsb held in each display pixel EX of thecorresponding row is discharged and this results in that the voltage(OV) in accordance with the display data is set between the gate and thesource of the transistor for the light emission driving.

The writing operation of the gradation sequence signal to the displaypixel EX of each row is repeated based on timing that the selectionsignal Ssel is applied to the selection line SL of each row. Thereby,the display data (the gradation sequence signal) is written in at leastplural rows of the display pixels EM arranged on the display panel 110,preferably, the all display pixels EM (refer to the opposite ends'potential Vc of the capacitor Cs of each display pixel in FIG. 20).(Light operation time period)

Subsequently, in the light emission operation time period TAem, as shownin FIG. 20, the selection signal Ssel is applied from the selectiondriver 120 to each selection line SL and the hold signal Shld is appliedfrom the hold driver 130 to each hold line HL at the off level. Thereby,the display pixel EM of each row is set at the no-selection state andthe no-holding state.

In addition, by applying the high level supplying voltage Vsc (=Ve) toat least plural rows of the display pixels EM, preferably, the alldisplay pixels EM from the supplying voltage driver 150 insynchronization with this timing, at least plural rows of the displaypixels EM, preferably, the all display pixels EM are set at the lightemission state.

Thereby, the light emission drive current Iem in accordance with thedisplay data (the gradation sequence signal) is generated on the basisof the voltage component held in each display pixel EM (between the gateand the source of the transistor for the light emission driving) to besupplied to the light emission element (the organic EL element OEL).

In other words, in the display pixel EM in which the gradation sequencesignal (the gradation sequence current Idata) in accordance with thenormal gradation sequence operation (other than the no-light emissiondisplay), the light emission drive current Iem having the current valuealmost the same as this gradation sequence current Idata is generated tobe supplied to the light emission element (the organic EL element OEL).Then, the light emission operation is carried out at a predeterminedluminance gradation sequence in accordance with the display data (referto the light emission drive current Iem in the display pixel EM at jthcolumn of first row in FIG. 20).

On the other hand, in the display pixel EM in which the gradationsequence signal (the no-light emission display voltage Vzero) inaccordance with the no-light emission display operation is written,since the gate-to-source voltage (the opposite ends' potential Vc of thecapacitor Cs) of the transistor for the light emission driving is setnot more than the threshold value (0V), the light emission drive currentIem is not supplied to the light emission element (the organic ELelement OEL) and this light emission element is held at the no-lightemission state (refer to the light emission drive current Iem in thedisplay pixel EM at jth column of second row in FIG. 20).

Such light emission operations (or the no-light emission operations) aresimultaneously carried out in at least plural rows of the display pixelsEM arranged on the display panel 110, preferably, to the all displaypixels EM. Thereby, the predetermined image information on the basis ofthe image signal is displayed on the display panel 110.

In this way, according to the display unit and its display drive methodof the embodiment, supplying the gradation sequence current Idata on thebasis of the display data (the image signal) to each display pixel otherthan the case of the no-light emission display and controlling the lightemission drive current to be supplied to the light emission element (theorganic EL element) based on the display data held in accordance withthis current value, it is possible to apply the drive control method ofthe current designation system to make the light emission element toperform the light emission operation at a predetermined luminancegradation sequence in accordance with the display data. In addition,both of the function (the current/voltage conversion function) toconvert the current level of the gradation sequence current Idata intothe voltage level by a single transistor (the drive transistor Tr 13)for the light emission driving provided to each display element and thefunction (the light emission drive function) to supply the lightemission drive current Iem having a predetermined current value on thebasis of the voltage level are provided. Therefore, it is possible torealize a desired light emission property stably for a long time withoutthe affection such as variation of the operational property and thetemporal change of the thin film transistor configuring the lightemission drive circuit in each display pixel.

In addition, according to the display unit and its display drivingmethod of the embodiment, the precharge operation and the voltagecorrection operation are carried out prior to the writing operation ofthe display data into each display pixel (the panel writing operation)and the light emission operation of the light emission element.Consequently, it is possible to set the transistor for the lightemission driving at the state that the electric charges equivalent tothe minimum luminance voltage having the voltage value, of whichabsolute value is larger than the absolute value of the thresholdvoltage of the transistor, is accumulated and held in advance betweenthe gate and the source of the transistor for the light emission driving(the drive transistor Tr 13 ). As a result, in the writing operation ofthe display data, it is not necessary to charge the electric chargesthat is the voltage, of which absolute value is larger than the absolutevalue of the threshold voltage, between the gate and the source (thecapacitor Cs) of the transistor for the light emission driving by thegradation sequence current Idata based on the display data. In addition,it is only necessary to add and accumulate (charge) only the voltagecomponent Vdata in accordance with this display data (the gradationsequence current Idata) so as to be capable of quickly and appropriatelywriting the voltage component based on the display data.

Accordingly, even upon the low luminance gradation sequence display thatthe gradation sequence in accordance with the display data is verysmall, it is possible to quickly and appropriately write the voltagecomponent based on the display data. As a consequence, it is possible toprevent the generation of the short f writing in each display elementand the desired image information can be displayed at the appropriateluminance gradation sequence in accordance with the image signal.

In addition, upon the no-light emission display, by supplying thepredetermined no-light emission display voltage Vzero based on thedisplay data (the image signal) to each display pixel, it is possible todischarge almost all of the electric charges (the voltage components)held between the gate and the source (the capacitor Cs) of thetransistor for the light emission driving. Therefore, by controlling thetransistor for the light emission driving not to supply the lightemission drive current to the light emission element (the organic ELelement, the transistor can be set at the no-light emission state andthe no-light emission operation can be realized well.

Further, according to the display unit and its display drive method, theprecharge operation and the voltage correction operation are carried outsimultaneously with respect to at least plural rows of the displaypixels, preferably, the all display pixels in prior to the panel writingoperation to write the display data in each display pixel arranged inthe display panel. Accordingly, it is possible to hold the voltagecomponent, of which absolute value is larger than the absolute value ofthe threshold voltage, etween the gate and the source of the transistorfor he light emission driving provided in each display ixel (the lightemission drive circuit) for very short time. Therefore, the panelwriting operation time period and the light emission operation timeperiod for one frame time period (about 16.7 msec) that has been definedin advance can be set relatively long and it is possible to realize theimage display of a good display image quality preventing deteriorationof the light emission luminance.

According to the embodiment, the case that the drive control methodshown in the second example is applied as the display drive method ofthe display unit and the voltage correction operation to accumulate theelectric charges equivalent to the minimum luminance voltage (itsabsolute value is larger than the absolute value of the thresholdvoltage) in each display pixel (between the gate and the source of thetransistor for the light emission driving) is carried out prior to thepanel writing operation is described. However, the present invention isnot limited to this. For example, as the drive control method shown inthe first example, it is obvious that the threshold correction operationto accumulate the electric charges equivalent to the threshold voltageof the transistor for the light emission driving provided in eachdisplay pixel (the light emission drive circuit) may be carried out.

In the embodiment, the drain of the hold transistor Tr 11 of the lightemission drive circuit DC is connected to the supplying voltage line VL.However, the present invention is not limited to this. As shown in FIG.21, the drain can function in the same way even if the drain isconnected to the hold line HL.

In addition, according to the embodiment, the no-light emission displayvoltage Vzero is the selection voltage value Vs. However, if thetransistor for the light emission driving does not supply the currentbetween the drain and the source even by the threshold variation whenthe potential of the supplying voltage Vsc is modulated from theselection voltage value Vs into the light emission voltage value Vs inthe light emission operation time period Tem, the no-light emissiondisplay voltage Vzero may be not different form the selection voltagevalue Vs.

In the display unit according to the present embodiment, any of the holdtransistor Tr 11, the selection transistor Tr 12, and the drivetransistor Tr 13 is a thin film transistor of an n-channel amorphoussilicon. However, it may be a polysilicon thin film transistor or all ofthem may be n-channel types or all of them may be p-channel types. Inthe case where all of them are p-channel types, it is only necessarythat high and low at the on level and the off level of the signal areinversed.

1. A light emission drive circuit for supplying a light emission drivecurrent to make a light emission element perform light emission,comprising: an electric charge accumulating section for accumulatingelectric charges on the basis of a gradation sequence signal designatinga luminance gradation sequence; a light emission control section forflowing a light emission drive current having a current value inaccordance with an amount of the electric charges accumulated in theelectric charge accumulating section; a writing control section forcontrolling a supplying state of the electric charges based on thegradation sequence signal to the electric charge accumulating section onthe basis of a first control signal; and a voltage control section forcontrolling a drive voltage for operating the light emission controllingsection on the basis of a second control signal.
 2. The light emissiondrive circuit according to claim 1, wherein the light emission controlsection has a drive transistor including a current path and a controlterminal, in which a current value of the light emission drive currentis set due to a potential difference between the control terminal andone end of the current path.
 3. The light emission drive circuitaccording to claim 1, wherein the light emission control section has adrive transistor including a current path and a control terminal, thedrive transistor flowing the light emission drive current of the currentvalue, which is based on the current value of the writing currentflowing through the current path in a light emission operation timeperiod as the gradation sequence signal in a writing operation timeperiod.
 4. The light emission drive circuit according to claim 1,wherein the light emission control section has a drive transistorincluding a current path and a control terminal, the drive transistorapplying a voltage that attains to a saturated range to one end and theother end of a current path in a light emission operation time period.5. The light emission drive circuit according to claim 2, wherein aprecharge voltage exceeding a threshold value of the drive transistor isapplied to the electric charge accumulating section.
 6. The lightemission drive circuit according to claim 5, wherein the writing controlsection partially discharges the electric charges accumulated in theelectric charge accumulating section on the basis of the prechargevoltage and remains the electric charges equivalent to the thresholdvoltage of the drive transistor.
 7. The light emission drive circuitaccording to claim 2, wherein a precharge voltage exceeding the minimumluminance value necessary for generating the light emission drivecurrent required for making the light emission element perform the lightemission operation at the minimum luminance gradation sequence isapplied to the electric charge accumulating section.
 8. The lightemission drive circuit according to claim 7, wherein the writing controlsection partially discharges the electric charges accumulated in theelectric charge accumulating section on the basis of the prechargevoltage and remains the electric charges equivalent to the minimumluminance electric charges.
 9. The light emission drive circuitaccording to claim 2, wherein the electric charge accumulating sectionis provided with a gradation sequence signal via the writing controlsection or the light emission control section.
 10. The light emissiondrive circuit according to claim 1, wherein the gradation sequencesignal is a gradation sequence current having a current value for makingthe light emission element perform the light emission operation at adesired gradation sequence.
 11. The light emission drive circuitaccording to claim 1, wherein the gradation sequence signal is agradation sequence current having a predetermined current value formaking the light emission element perform the no-light emissionoperation.
 12. The light emission drive circuit according to claim 5,wherein the precharge voltage and the gradation sequence signal aresupplied to the electric charge accumulating section at differenttiming.
 13. The light emission drive circuit according to claim 1,wherein the gradation sequence signal is a gradation sequence currenthaving a current value for making the light emission element perform thelight emission operation at a predetermined luminance gradation sequenceor a gradation sequence voltage having a predetermined voltage value formaking the light emission element perform the no-light emissionoperation, and one of the gradation sequence current and the gradationsequence is selectively applied to the electric charges accumulationsection.
 14. The light emission drive circuit according to claim 2,wherein the writing control section has a selection transistor includinga current path to which a precharge voltage of which absolute value islarger than the absolute value of the threshold voltage of the drivetransistor or larger than the absolute value of the minimum luminancevoltage necessary for generating the light emission drive currentrequired for making the light emission element perform the lightemission operation at the minimum luminance gradation sequence, and thegradation sequence signal are selectively supplied; and a controlterminal to which the first control signal is applied.
 15. The lightemission drive circuit according to claim 2, wherein the voltage controlsection has a hold transistor including a current path of which one endside is provided with the supplying voltage and of which other end sideis connected to the control terminal of the drive transistor and one endside of the electric accumulating section; and a control terminal towhich the second control signal is applied.
 16. A light emission circuitcomprising: a selection line; a hold line; is a data line; a supplyingvoltage line; a hold transistor having a gate electrically connected tothe hold line, and a current path; a drive transistor having a gate anda current path, the gate of the drive transistor being electricallyconnected to one end of the current path of the hold transistor and oneend of the current path of the drive transistor being connected to thesupplying voltage line; and a selection transistor having a gate and acurrent path, the gate of the selection transistor being electricallyconnected to the selection line, one end of the current path of theselection transistor being connected to the other end of the currentpath of the drive transistor, and the other end of the current path ofthe selection transistor being connected to the data line.
 17. The lightemission drive circuit according to claim 16, wherein different controlsignals are outputted to the selection line and the hold line,respectively.
 18. The light emission drive circuit according to claim16, wherein the selection transistor is turned on by a first controlsignal from the selection line in a precharge time period, the holdtransistor is turned on by a second control signal from the hold line,and a voltage of which absolute is larger than the absolute value of thethreshold voltage of the drive transistor or a voltage exceeding theminimum luminance voltage necessary for generating the light emissiondrive current required for making the light emission element perform thelight emission operation at the minimum luminance gradation sequence isprovided to the drive transistor; and the selection transistor is turnedoff by the first control signal from the selection line in a correctionoperation time period, and the voltage between the gate of the drivetransistor and the other end of the current path of the drive transistoris set so as to decrease to the threshold voltage of the drivetransistor or the minimum luminance voltage.
 19. A drive control methodof a light emission drive circuit, which supplies a light emission drivecurrent to a light emission element to make the light emission elementperform the light emission, comprising: setting a first potentialdifference equivalent to a threshold value of a transistor element, or afirst potential difference equivalent to the minimum luminance voltagenecessary for generating the light emission drive current required formaking the light emission element perform the light emission operationat the minimum luminance gradation sequence between a gate and a sourceof a transistor element to supply the light emission drive current tothe light emission element; applying a gradation sequence signal to makethe light emission element perform the light emission operation at aluminance gradation sequence to the transistor element and setting asecond potential difference in accordance with the luminance gradationsequence between the gate and the source of the transistor element; andturning on the transistor element at a predetermined conducting state onthe basis of the second potential difference, generating the lightemission drive current having a current value in accordance with theluminance gradation sequence, and supplying it to the light emissionelement.
 20. The drive control method according to claim 19, whereinsetting the first potential difference includes a step of setting athird potential difference on the basis of a precharge voltage of whichabsolute value is larger than that of the threshold voltage or a thirdpotential difference on the basis of the precharge voltage of whichabsolute value is larger than that of the minimum luminance voltagebetween the gate and the source of the transistor element; and a step ofturning on the transistor element on the basis of the third potentialdifference and setting the potential difference between the gate and thesource of the transistor element at the first potential difference. 21.The drive control method according to claim 19, wherein setting thesecond potential difference includes a step of adding electric chargesof the first potential difference between the gate and the source of thetransistor element to electric charges accumulated based on a gradationsequence current applied to the transistor element, the gradationsequence current as the gradation sequence signal having a current valuefor making the light emission element perform the light emissionoperation at a desired luminance gradation sequence.
 22. The drivecontrol method of the light emission drive circuit according to claim19, wherein setting the second potential difference includes dischargingelectric charges based on the first potential difference held betweenthe gate and the source of the transistor element by applying agradation sequence voltage as the gradation sequence signal having apredetermined voltage for making the light emission element perform theno-light emission operation.
 23. A display unit comprising: a pluralityof display pixels each of which includes a light emission element and alight emission drive circuit having an electric charge accumulatingsection for accumulating electric charges based on a gradation sequencesignal to designate a luminance gradation sequence in accordance withdisplay data, a light emission control section for generating a lightemission drive current having a predetermined current value inaccordance with the electric charges accumulated in the electric chargeaccumulating section and supplying the light emission drive current tothe light emission element, a writing control section for controllingthe supplying state of the electric charges based on the gradationsequence signal to the electric charge accumulating section, and avoltage control section for controlling a drive voltage for making thelight emission control section perform the operation, respectively; aselection line in which a writing control signal for controlling theoperation state of the writing control section of the each display pixelis applied; a hold line in which a voltage control signal forcontrolling the operation state of the voltage control section of theeach display pixel is applied; and a data line to which the gradationsequence is supplied.,
 24. The display unit according to claim 23, whichfurther comprising a selection driver which applies the writing controlsignal in the selection line; a hold driver which applies the writingcontrol signal in the hold line; and a data driver which supplies thegradation sequence signal to the data line.
 25. The display unitaccording to claim 23, wherein the electric accumulating sectionincludes a capacitance element, the light emission control sectionincludes a drive transistor, wherein one end side of a current paththrough which the light emission drive current flows is connected to thelight emission element and further, is connected to one end side of thecapacitance element; a supplying voltage for flowing the light emissiondrive current is applied to the other end side of the current path; anda control terminal for controlling the supplying state of the lightemission drive current is connected to the other end side of thecapacitance element, the writing control section includes a selectiontransistor, wherein one end side of a current path is connected to thedata line, the other end side of the current path is connected to theone end side of the capacitance element; and a control terminal isconnected to the selection line, and the voltage control sectionincludes a hold transistor, wherein one end side of a current path isconnected to the other end side of the capacitance element and a controlterminal is connected to the hold line.
 26. The display unit accordingto claim 25, wherein the light emission control section generates thelight emission drive current having the predetermined current value,wherein the drive transistor is turned on at a predetermined conductingstate in accordance with the potential difference based on the electriccharges accumulated in the capacitance element.
 27. The display unitaccording to claim 25, further comprising a supplying voltage driver forapplying the supplying voltage to the other end side of the current pathof the drive transistor.
 28. The display unit according to claim 27,wherein the supplying voltage driver applies the supplying voltage tothe control element of the drive transistor.
 29. The display unitaccording to claim 24, wherein the data driver applies a prechargevoltage exceeding the threshold value of the drive transistor to thedata line, and the light emission drive circuit applies the prechargevoltage applied to the data line to the electric charge accumulatingsection via the writing control section.
 30. The display unit accordingto claim 29, wherein the light emission drive circuit partiallydischarges the electric charges accumulated in the electric chargeaccumulating section on the basis of the precharge voltage and remainsthe electric charges equivalent to the threshold voltage of the drivetransistor.
 31. The display unit according to claim 24, wherein the datadriver applies a precharge voltage exceeding the minimum luminance valuenecessary for generating the light emission drive current required formaking the light emission element perform the light emission operationat the minimum luminance gradation sequence to the data line; the lightemission drive circuit applies the precharge voltage applied to the dataline to the electric charge accumulating section via the writing controlsection.
 32. The display unit according to claim 31, wherein the lightemission drive circuit partially discharges the electric chargesaccumulated in the electric charge accumulating section on the basis ofthe precharge voltage, remains the electric charges equivalent to theminimum luminance electric charge, and holds this electric charge. 33.The display unit according to claim 24, wherein the light emission drivecircuit applies the gradation sequence signal applied from the datadriver to the data line to the electric accumulating section via thewriting control section.
 34. The display unit according to claim 33,wherein the gradation sequence signal is a gradation sequence currenthaving a predetermined current value for making the light emissionelement perform the light emission operation at a desired luminancegradation sequence on the basis of the display data; and the electriccharges in accordance with the gradation sequence current is accumulatedin the electric accumulating section.
 35. The display unit according toclaim 33, wherein the gradation sequence signal is a gradation sequencevoltage having a predetermined current value for making the lightemission element perform the no-light emission operation on the basis ofthe display data; and the electric charges accumulated in the electricaccumulating section are discharged in accordance with the gradationsequence voltage.
 36. The display unit according to claim 29, whereinthe precharge voltage and the gradation sequence signal applied from thedata driver to the data line are applied in the electric chargeaccumulating section via the writing control section at different timingrespectively.
 37. The display unit according to claim 35, wherein thedata driver applies the gradation sequence current and the gradationsequence voltage to the data line selectively.
 38. A display having: aselection line; a hold line; a data line; a supplying voltage line; ahold transistor, in which a gate is connected to the hold line; a drivetransistor having a gate and a current path, the gate of the drivetransistor being connected to one end of a current path of the holdtransistor, and one end of the current path of the drive transistorbeing connected to the supplying voltage line; a selection transistorhaving a gate and a current path, the gate of the selection transistorbeing connected to the selection line, one end of the current path ofthe selection transistor being connected to the other end of the currentpath of the drive transistor, and the other end of the current path ofthe selection transistor being connected to the data line; a lightemission element which is connected to the other end side of the currentpath of the drive transistor; a selection driver which outputs aselection signal to the selection line; a hold driver which outputs ahold signal to the hold line; a data driver which supplies a gradationsequence signal to the data line; and a supplying voltage driver whichoutputs a supplying voltage to the supplying voltage line.
 39. A displaydrive method of a display unit which comprises a display panel made by aplurality of display pixels and makes the each display pixel perform thelight emission operation at a predetermined luminance gradation sequenceby supplying a gradation sequence signal designating a luminancegradation sequence in accordance with the display data to the eachdisplay pixel, and displays desired image information on the displaypanel, the method comprising setting at least part of the plural displaypixels at a selection state, and setting a first potential differenceequivalent to a threshold voltage of a transistor element or a firstpotential difference equivalent to the minimum luminance voltagenecessary for generating the light emission drive current required formaking the light emission element perform the light emission operationat the minimum luminance gradation sequence between one end of a gateand one end of a current path of a transistor element for supplying alight emission drive current to a current-controlled type of a lightemission element provided in the each display pixel; sequentiallysetting the display pixel for each row of the display panel at aselection state, sequentially applying a gradation sequence signal formaking the light emission element of the each display pixel perform thelight emission operation at a predetermined luminance gradation sequencein accordance with the display data, and setting a second potentialdifference in accordance with the luminance gradation sequence between agate and one end of a current path of the transistor element; andsetting at least part of the plural display elements arranged on thedisplay panel at a no-selection state, turning on the transistor elementof the each display element on the basis of the second potentialdifference, and individually generating the light emission drive currenthaving a current value in accordance with the luminance gradationsequence for the each light emission element and supplying the lightemission current to the each light emission element.
 40. The displaydrive method according to claim 39, wherein setting the first potentialdifference in the each display pixel includes: a step of setting atleast part of the plural display elements at a selection state andsetting a third potential difference based on a precharge voltage ofwhich absolute value is larger than the absolute value of the thresholdvoltage or a third potential difference based on the precharge voltageof which absolute value is larger than the absolute value of the minimumluminance voltage between one end of a gate and one end of a currentpath of the transistor element of the each display pixel; and a step ofsetting at least part of the plural display elements at a no-selectionstate, turning on the transistor element based on the third potentialdifference set in the each display pixel, and setting the firstpotential difference between one end of the gate and one end of thecurrent path of the transistor element.
 41. The drive control method ofthe display unit ccording to claim 39, wherein the step of setting theecond potential difference includes a step of adding electric charges ofthe first potential difference between the gate and the source of thetransistor element to electric charges accumulated based on a gradationsequence current applied to the transistor element, the gradationsequence current as the gradation sequence signal has a current valuefor making the light emission element perform the light emissionoperation at a desired luminance gradation sequence.
 42. The displaydrive method of the display unit according to claim 39, wherein the stepof setting the second potential difference includes a step ofdischarging electric charges based on the first potential differenceheld between the gate and the source of the transistor element byapplying a gradation sequence voltage as the gradation sequence signalhaving a predetermined voltage for making the light emission elementperform the no-light emission operation.
 43. A light emission drivecircuit for flowing a light emission drive current to make a lightemission element perform light emission, comprising: electric chargeaccumulating section for accumulating electric charges on the basis of agradation sequence signal designating a luminance gradation sequence;light emission control section for flowing a light emission drivecurrent having a current value in accordance with the electric chargesamount accumulated in the electric charge accumulating section; andvoltage setting section for partially discharging the electric chargesaccumulated in the electric charge accumulating section in order for thelight emission control section to set the light emission drive currentat the current value.
 44. A drive control method of a light emissiondrive circuit for flowing a light emission drive current to make a lightemission element perform light emission, comprising: a first potentialdifference step of setting a first potential difference on the basis ofa precharge voltage that is larger than the minimum luminance gradationsequence necessary for generating the light emission drive currentrequired for making the light emission element perform the lightemission operation at the minimum luminance gradation sequence or athreshold potential difference between the control terminal and one endof a current path of a drive transistor in which a current value of thelight emission drive current is set by a potential difference between acontrol terminal and one end of the current path of the drivetransistor; a second potential difference step of setting a secondpotential difference equivalent to the minimum luminance potentialdifference or the threshold potential difference between the controlterminal and one end of the current path of the drive transistor afterturning on the drive transistor on the basis of the first potentialdifference; and a third potential difference step of setting a thirdpotential difference equivalent to the luminance gradation sequencebetween the control terminal and said one end of the current path of thedrive transistor by applying a gradation sequence signal for making thelight emission element to perform the light emission operation at adesired luminance gradation sequence and flowing the gradation sequencesignal to the current path of the drive transistor.
 45. A display unitcomprising: a plurality of display pixels including a light emissionelement; and a light emission drive circuit having an electric chargeaccumulating section to accumulateelectric charges based on a gradationsequence signal to designate a luminance gradation sequence inaccordance with the display data, a light emission control section togenerate a light emission drive current having a current value inaccordance with the electric charges accumulated in the electric chargeaccumulating section and supplying the light emission drive current tothe light emission element, and a voltage setting section to dischargethe electric charges accumulated in the electric charge accumulatingsection in order for the light emission control section to set the lightemission drive current at the current value, respectively.
 46. A displaydrive method of a display unit for making light emission elements of aplurality of display pixels to perform the light emission arranged in arow direction and a column direction, comprising: a first potentialdifference step of setting the display pixel at a selection state andsetting a first potential difference on the basis of a precharge voltagethat is larger than the minimum luminance gradation sequence necessaryfor generating the light emission drive current required for making thelight emission element perform the light emission operation at theminimum luminance gradation sequence or a threshold potential differencebetween the control terminal and one end of a current path of a drivetransistor which can supply a light emission drive current to the lightemission element; a second potential difference step of setting a secondpotential difference equivalent to the minimum luminance potentialdifference or the threshold potential difference between the controlterminal and one end of the current path of the drive transistor elementin a state of turning on the drive transistor on the basis of the firstpotential difference; a third potential difference step of setting athird potential difference equivalent to the luminance gradationsequence between the control terminal and said one end of the currentpath of the drive transistor by applying a gradation sequence signal formaking the light emission element to perform the light emissionoperation at a desired luminance gradation sequence and flowing thegradation sequence signal to the current path of the drive transistor;and a light emission step that the drive transistor flows the lightemission drive current on the basis of the gradation sequence signal tothe light emission element by applying a voltage so that a potentialdifference between said one end and the other end of the current path ofthe drive transistor is saturated.
 47. A light emission drive circuit,comprising: a light emission control section having a current path offlowing a light emission drive current from the current path; anelectric charge accumulating section to accumulate electric charges inaccordance with a current value of a current flowing through the lightemission control section; a voltage setting section to supply a currentof a current value that allows the light emission element to perform thelight emission operation at a luminance other than the no-lightluminance gradation sequence and accumulating the electric chargesequivalent to the luminance gradation sequence in the electric chargeaccumulating section; and a gradation sequence setting section todischarge the electric charges in the electric charge accumulatingsection such that the light emission element is made into the no-lightemission state or the electric charges such that the light emissiondrive current does not flow.
 48. A drive control method of a lightemission drive circuit for flowing a light emission drive current tomake a light emission element perform light emission, comprising: afirst potential difference step of generating a first potentialdifference between the control terminal and one end of the current pathof a drive transistor before a luminance gradation sequence signal isapplied to a drive transistor, the first potential difference beingirrelevant to the current value the luminance gradation sequence signaland allows the light emission element to perform the light emissionoperation at a luminance gradation sequence other than a no-lightemission luminance gradation sequence; and a second potential differencestep of generating a second potential difference between the controlterminal and the one end of the current path of the drive transistor sothat the light emission element performs the no-light emission state onthe basis of a no-light emission luminance gradation sequence signalapplied to the drive transistor when the luminance gradation sequencesignal is the no-light emission luminance gradation sequence signal. 49.A display unit comprising: a plurality of display pixels comprising; alight emission element; and a light emission drive circuit having alight emission control section to apply a light emission drive currentfrom the current path to the light emission element, an electric chargeaccumulating section to accumulate electric charges in accordance withthe current value of the current flowing the light emission controlsection, and a voltage setting section to accumulate the electriccharges equivalent to the luminance gradation sequence in the electriccharge accumulating section, respectively; and a gradation sequencesetting section to discharge the electric charges accumulated in theelectric charge accumulating section so that a state of the electriccharges allowing the light emission element to perform the lightemission operation at a luminance gradation sequence other than ano-light emission luminance gradation sequence is changed into a stateof the electric charges allowing the light emission element to performthe no-light emission state or the light emission drive current not toflow.
 50. A display drive method of a display unit for making lightemission elements of a plurality of display pixels to perform the lightemission arranged in a row direction and a column direction, comprising:a first potential difference step of generating a first potentialdifference between the control terminal and one end of the current pathof a drive transistor before a luminance gradation sequence signalapplied to a drive transistor, the first potential difference isirrelevant to the current value the luminance gradation sequence signaland allows the light emission element to perform the light emissionoperation at a luminance gradation sequence other than a no-lightemission luminance gradation sequence; and a second potential differencestep of generating a second potential difference between the controlterminal and the one end of the current path of the drive transistor sothat the light emission element performs the no-light emission state onthe basis of a no-light emission luminance gradation sequence signalapplied to the drive transistor when the luminance gradation sequencesignal is the no-light emission luminance gradation sequence signal.